In The Short Victorious War Harrington learns the reason Young was not removed from command after the events in On Basilisk Station. He used a loophole to give his return to the shipyard for repairs a legal basis.
At the end of the prequel short story "Let's Dance!" from In Fire Forged, the First Space Lord has been pressured into relieving Honor Harrington from command of the Hawkwing for cooperating with the Audubon Ballroom to take down a slave depot. He proceeds to reassign her to the Advanced Tactical Course, also known as "the fast-track to senior command".
In In Enemy Hands, Thomas Theisman tries to appeal to the international law of the Deneb Accords to secure fair treatment of Prisoners of War from the otherwise sadistic Cordelia Ransom. Ransom uses his own logic to find a way to Loophole Abuse the Accords into letting her do what she wants anyway, only making it completely legal, and Theisman spends the rest of the night puking over what he's just unwittingly done.
Another loophole was used in the Andermani Empire following the removal of the mentally unstable Emperor Gustav VI. With no living brothers or sons, and a potential civil war on hand, his oldest sister had herself declared legally a man, took control of the navy and essentially dared any of her cousins to challenge her right to reign as Gustav VII.
This is how the Obstructive Bureaucrats of the Solarian League gained power: Their constitution gave every member nation of the League veto power over statutes... but not over regulations, which is what the bureaucrats used.
Dune: can be applied to using outlawed weapons, but is a legal gray/grey area.
In the Dune universe, there is a major prohibition against using nuclear weapons against human targets. Just before the final battle, Muad'Dib uses a nuke to blow a hole in a large rock formation so his army can pass through. He points out that no humans were killed by the nuke.
In Thief of Time, one Auditor who's assumed a human body finds she can overcome the compulsion to obey rules by declaring that certain things are "bloody stupid"; "bloody stupid" things can be safely ignored. This was written into the rules because regular auditors were paralyzed with indecision if confronted with a paradoxical statement, like a sign saying "Ignore this sign", or a sign next to an empty cage that says "do not feed the elephant".
At the climax of the book, the horsemen of the Apocalypse must ride out at the end of the world. No-one ever said against whom.
Susan's thought process in Soul Music, on the subject of leaving school without permission:
There's going to be trouble over this. ... I'm on the back of a horse a hundred feet up in the air, being taken somewhere mysterious that's a bit like a magic land with goblins and talking animals. There's only so much more trouble I could get into... Besides, is riding a flying horse against school rules? I bet it's not written down anywhere.
Likewise with Gnome Watch officer Buggy Swires; in a companion book, he is said to have a natural resistance to rules and authority. Even the unwritten rules like "Do not attempt to eat this Giraffe" or "don't kick people in the head because they won't give you a chip".
In Discworld, the laws of nature work like this; Ponder Stibbons has discovered that, like a busy local authority, the universe has failed to forbid a lot of things simply because it never occurred to it anyone would do them. The trick is to get things done before the universe rewrites the rulebook and pretends it was impossible all along. The breakthrough came with the invention of Hex, which can repeat the same spell several times a minute in minutely different ways, the universe making each one impossible just too late, allowing him to (for example) assemble the texts of books that haven't yet been written.
The climax of Unseen Academicals hinges on a long-forgotten, sometimes-derided football rule specifying that the first object handled by three consecutive players in a game shall be considered the ball. This allows the young hero to put his tin-can-kicking skills to brilliant use when the original game ball is "lost."
In the City Watch books there's a few loopholes in the traditional watchmen's oath, which requires new recruits to swear to "uphold the Laws and Ordinances of the city of Ankh-Morpork, serve the public trust, and defend the subjects of His/Her Majesty". As many fans have noticed, there's nothing in there about defending the ruler (just his/her subjects), and in Night Watch Vimes points out it doesn't say anything about following orders.
This trope is how the Librarian is able to keep his job at Unseen University, despite his transformation; There's no rule barring an orangutan from the college council, though the wizards had looked very hard for one. This also enables him to read the Necrotelecomnicon without harm; it contains things manwas not meant to know, nobody said anything about apes.
While acting as the eponymous Hogfather, Death saved the life of a girl destined to die and responded calmly when Albert protested it was against the rules for Death to do such.
In The Heroes of Olympus by Rick Riordan, the Amazons get their queens crowned by fights to the death. Given the whole death thing, there's no law against repeat matches- so when an old queen comes back from the dead wanting a rematch (and being able to return even if she dies in battle), you can bet that Hylla was going to get out her law-fu ASAP.
In The Zucchini Warriors by Gordon Korman, Cathy from the girls' boarding school across the street pulls a Sweet Polly Oliver and serves as quarterback, leading the team to victory. Naturally, once it's found out, the team coach attempts to argue that girls can too play football (despite having said in a prior interview that they can't). The referee shuts this down by pointing out that, as this is the Macdonald Hall football team and Cathy is not a student there, she's not eligible to play.
Early in Raymond E. Feist's Daughter Of The Empire, the main character, Mara, is attacked by an assassin on a spot in her home that, under the law, only members of her family can go on pain of death. She's rescued by a soldier but, even though he saved her life, he still needs to be executed for trespassing. She declares that he will be executed... someday, at an undetermined point in the future. This basically lets him off completely and it also means that, since he's technically a dead man walking, he can get away with things (like manhandle an irritating nobleman), that would ordinarily get him killed on the spot. In fact, the core concept behind Mara's rise from minor noblewoman to the most important person in the Empire was her realization that violating tradition wasn't illegal. This allowed her to recruit a large number of people who traditionally required to act as outlaws, but never technically been outlawed, such as hundreds of highly competent soldiers whose masters had been killed and the head of the Empire's top spy network.
In one of the Dinotopia books (Lost City), the newcomers to the lost Troodon warrior haven of Halcyon are challenged to complete either an underground maze or an obstacle course against one of the residents. The rules of the obstacle course are, simply, to get from one end to the other before the opponent completes his own course... but the honor-bound saurians had never previously considered the strategy of avoiding all of the obstacles and running down the empty ground between the two courses...
In the same book, two high-ranking officials play an oral wargame, declaring what they order their troops and what not. It eventually gets down to the generals preparing to go one on one on a bridge. Then the villain claims the Kraken rises up from the water and grabs his opponent. In retaliation his opponent declares that the Kraken isn't a bloodthirsty monster, but just wants a friend. The Judges declare it legal, and the villain loses.
In The False Mirror, Ranji-aar's team was going through a large maze and discovered that the other team had bribed people, and had learned the route. So they made a ladder to get up on top of the walls, away from all the obstacles, and fake environmental dangers. Needless to say they won.
Enderís Game. Ender is faced with a horribly unbalanced game against two teams at once. Ender wins due to the victory condition just being opening the enemy's gate, without bothering to actually fight the enemy soldiers.
This was very deliberately done, a big deal is later made about war having no rules, and anything you can do to win is what you should do. (Apparently a war to extinction against aliens has no Geneva Convention). Later, while he's playing a simulation in which he was leading a campaign against the Buggers, the final confrontation gave him only a few, old ships against the Buggers' home planet surrounded by warships. He blows up the planet. And then it wasn't a simulation after all...
One of the final exams in Robin Hobb's Shamans Crossing is a test of bridge construction. Turns out the actual test was simply "get your team across this river", which is most easily done by making them all swim. Nobody said making a bridge was mandatory.
Also happens near the end of her Fool's Fate, though in that case, the only thing saved was Dutiful's honor, as he had already broken his promise, made rather under duress, to kill a dragon - he instead set it free. Then someone realized his actual promise had only been to deliver the dragon's head to his betrothed's house - he had never promised it had to stay there, nor that it couldn't still be attached to said dragon. And thus, his promise was technically fulfilled.
In The Lives Of Christopher Chant, in order to rescue his friend Tacroy, Christopher has to find Tacroy's soul and claim it from the Priest-King (the Dright) who rules Tacroy's home dimension and owns everyone in it. When Christopher does see the soul, it immediately becomes much farther away from him. When Christopher claims the Sept is cheating, he casually points out that "I named no rules." At which point Christopher and Millie follow suit, because if there's no rule to say the Sept can't use magic to interfere, then there's no rule to say they can't use their magic to stop him interfering.
Immediately after this, the Dright asks for one of Christopher's lives in return for Tacroy's soul, but Christopher realizes that this will grant the Dright control over him. Chistopher thus gives the Dright one of his lives and immediately sets it on fire. (It did hurt a bit.)
In the children's novel Ralph S. Mouse by Beverly Cleary, Ralph's human friend, having discovered Ralph and his comparatively impressive intellect, decides to bring him to school for show and tell. The children decide to test his smarts by putting him in a maze with some food at the end and seeing how long it took him to get to the food. Ralph decides that the whole thing is stupid, climbs up the wall, and runs along the top of the maze to get to the food quicker. The children call loophole abuse, but instead of forcing the issue by covering the maze, they just put him back at the beginning, allowing Ralph to repeat his stunt over and over until the children get fed up and declare that, far from being smart, Ralph is too stupid to complete the maze by following the rules. Ralph and his human friend find this an unfair assessment, since they asked Ralph to get to the food as quick as possible and Ralph delivered repeatedly.
Deathly Hallows: The Elder Wand has passed from hand to hand when the previous owner is killed. Voldemort assumes that this is the only way to gain control of it. It's not. More specifically, it's only necessary to defeat/disarm the previous owner. Voldemort assumed that the Elder Wand had "passed to" Snape when he killed Dumbledore, but Malfoy disarmed him first, and when Harry later defeated Malfoy, the Elder Wand recognized him as its master. Even more specifically, ownership is passed only when the current owner is 'defeated/disarmed'. Dying without either of those conditions being met or arranging for one's suicide, even by help of another, means there is no transfer of ownership of the wand and its true power dies with the last owner. Dumbledore knew this, hence why he arranged his Mercy Killing with Snape. Malfoy was simply a Spanner in the Works in that regard.
In Chamber of Secrets, it's revealed that Arthur Weasley works in the Misuse Of Muggle Artifacts Office, but abuses Muggle artifacts on his own time. He purposefully wrote a loophole into the law in order to get away with this, namely it is misuse to use said object to harm or mislead a muggle. Personal experimentation in one's own home is another matter altogether.
Quidditch defies this trope by having a rule for everything. For example, there's a rule that forbids using a battle axe in play and that's just the tip of the iceberg. According to Quidditch Through the Ages, these rules arose because of this trope.
In Goblet of Fire, the rules for the first contest states that contestants can only bring a wand to face the dragons, but not that they can't use it to summon whatever else they need. Harry uses that loophole to summon his Firebolt flying broomstick.
Aes Sedai are bound by the Oath Rod "to speak no word that is not true," but the Oath Rod defines "true" as "what the speaker believes." Thus, an Aes Sedai who believes a lie can tell it as if it were the truth, and the Aes Sedai are experts at using this and other Loophole Abuses to twist the truth beyond recognition.
The third Oath "Never use the One Power as a weapon, except ... to save her own life, or her Warder's, or the life of another sister " can be circumvented by an Aes Sedai intentionally placing herself (or, presumably her Warder or another sister) in danger.
The danger has to be real and fatal, though (or at least the sister has to believe it is), meaning they can't exactly use this loophole to shatter armies with impunity the way they could without the Oath. The spirit of the law is upheld.
Under Tower Law the Amyrlin must be Aes Sedai, but you don't have to be Aes Sedai to become Amyrlin. Thus, raising Egwene as Amyrlin makes her legally Aes Sedai without having to raise her as Aes Sedai. For even more bonus points, they wouldn't legally have been able to raise any regular Aes Sedai without an Amyrlin.
The Eelfinn did this to Mat, when he unwittingly made his Three Wishes to them: "Wise to ask leavetaking when no terms were set, yet unwise not to set the terms. We will set the terms..."
Mat's foxhead medallion worked on a big loophole (proving the Eelfinn would have had a ball with D&D wishes) in that he was free of the One Power , in that the threads melts when they touched him directly, but if you picked up a pile of dung, for example, and threw it at him with the power, it still worked.
Mat, sadly, didn't learn his lesson well enough: in Towers of Midnight, he carefully binds the Eelfinn in a promise not to attack his party. Then there's a solid Oh, Crap moment when the packs of armed Aelfinn show up to block the way out.
Also in the first book, when she interprets a cry for help from someone who has no idea she's there as an "invitation" enabling her to enter a human building. She has to argue over this to her commander later, when she states that there is actually precedent for it.
Or in the third book, when joking (and unsuspecting) permission for Juliet to bring her "invisible friend" is also used as an invitation.
Earlier than that, even - when Artemis allows himself to be captured, Spiro gives him a tour of the building's security system to show him just how screwed he is. Artemis jokingly says he could beat the security with the help of his fairy friends. Spiro tells him he can bring in all the fairy friends he wants. Oops.
In the first book, Artemis makes the mistake of saying that no fairy may enter his house while he's alive. The fairies try to kill him first. And that's exactly what he wanted.
In the prequel story, LEPrecon, which shows how Holly got into the LEP. Her test is interupted by Turnball Root, and it ends up at a point where Commander Root and Trouble Kelp are locked inside a human dwelling. Holly can't go in to save them, so she gets the ship and tears the house down. You can't get dwelling sickness if there's no dwelling!
Redwall: Matthias, at the top of a bell tower, promises Big Bad Cluny he'll come down if Cluny releases his hostage. Ain't no rule that Matthias couldn't cut down the giant bell, which Cluny is directly under, before coming down.
Part of the backstory of David Gerrold's The War Against the Chtorr series is that the United States had severe arms limitations imposed on it after the last world war. There was no such restriction on weapons research. Therefore, the U.S. funneled tons of money into advanced weapon design programs and built modular factories that could be turned to war production with the flip of a switch.
In the second Flat Stanley book, Stanley ends up being used as a sail in a boat race. A judge is heard saying that it is not against the rules to use your teammate as a sail.
The Kid Who Ran For Principal by Judy K. Morris. Ain't no rule that says a student can't run for interim principal for the purpose of firing an ineffective and cruel teacher.
In the Thursday Next novel Something Rotten, Aint no rule saying a genetically re-engineered Neanderthal can't play croquet although it was in dispute; there are rules saying non-humans can't. The rule that non-humans cannot play croquet would normally have prevented him from playing, but the reconstruction involved using some human genes for the vocal cords. As a result of the small percent of human DNA, he wasn't technically non-human, so they let him play.
In the Next-World's version of croquet, finding loopholes in the rules is an expected part of gameplay and heartily enjoyed by the fans.
In the short story "Nothing in the Rules", one team at a girls' swimming competition contains a mermaid, who wins everything. In response to the opposition's outrage, the team coach points out that the rules only specify that all entrants must be female; nothing is said about species. The officials are reluctantly forced to admit that he's right. Whereupon the opposing coach visits the city zoo and borrows a female seal, who (properly incentivized with a bucket of fish) outswims the mermaid. To avoid disqualification for not using the proper swimming form, the mermaid only competes in the freestyle events.
In Throwback a genetically recreated prehistoric human becomes a football player. In this case any "humans only" rules don't apply because before the story began the recreated cavemen fought for their civil rights and were legally recognized as people, even though they are technically not the same species as most humans.
In Lois McMaster Bujold's Vorkosigan Saga, it is a frequently cited legal precedent that there ain't no rule a horse can't be a count's heir (or at least, there wasn't in Lord Midnight Vortala's time). If a horse's ass can be a Count, why not the whole horse? On the other hand, there Ain't No Rule against a Count hiring 2000 chefs, equipping them with Chef's knives and sending them after his enemies (Each Count can only legally have 20 of his own troops, total). The Emperor was not amused.
The POW camp in the short story Borders of Infinity applied this trope in a rather nasty manner. So many square meters per inmate? An opaque, luminous force shield encloses that much open ground and field latrines. No periods of darkness for over twelve hours? No darkness at all, ever. Water? Everyone gets a cup along with their clothes and a bedroll (the taps by the latrines work most of the time). Access to medical personnel? Plenty of medics mixed in with the general population, but they mentioned nothing about equipment. Food? A pile of ICRC-equivalent compliant ration bars (one per inmate) appear at a random location on the camp perimeter twice per day. No solitary confinement for more than 24 hours? <insert bitter laughter here> No beatings or rapes by guards? No guards....
Ain't no rule that a chicken can't be mayor. This one is from the book Herb Seasoning by Julian Thompson. Said chicken actually understands English and can write in (no pun intended) chicken scratch, but she's really being used as a figurehead for a conman. Long story, just read the book. Oh, and there Ain't No Rule that says the cure for depression can't be a mixture of eel slime and aspirin. Applied topically.
Used in Robert Asprin's Phule's Company, when the company competes on an obstacle course against the elite Red Eagles. The race specifies "full combat gear and conditions," and the Eagles make good time navigating the obstacles in heavy packs with loaded weapons. Then on their turn, Phule's company blows up the obstacles, and sprints straight through in record time. Some Eagles complain that this is cheating, but their own commander agrees that in "combat conditions," you're not worried about being polite to the landscape.
In book five, he bets Sweyn that he can catch a bigger trout with a pole, line, hook, and worm bait, than Sweyn can with his rod, reel, and fly hooks. Then he tells J.D. that there ain't no rule against setting up six poles at once.
In book seven, he bets that Parley Benson's quarter horse can't beat Sweyn's mustang in a mile race. He wins this bet easily since Parley's horse hasn't the stamina, then proposes to give the kids a chance to win their money back by swapping horses and racing again. When he wins on the other horse, the kids accuse him of cheating, and he tells them that there ain't no rule against slowing a horse to let it get its wind, and that if Parley had done it, they certainly wouldn't have complained.
In The Dresden Files, there are lots of different sets of rules that must be followed. As expected, many of the characters spend a lot of time finding loopholes in them:
In Dead Beat, he gets away with necromancy because technicallythe Fifth Law of Magic only applies to human dead, not Tyrannosaurs. It probably helped that it was both necessary to saving the world and downright awe-inspiring.
The Sidhe (the "fairy lords") are physically incapable of lying or breaking their word, but they are basically made of loophole abuse. Some notable examples include:
Harry's crazy godmother Lea swears to give Harry a temporary break from trying to take him captive so he can go save the world. She explicitly does not swear not to send one of her minions to do it for her.
Part of Harry's deal with Mab, to perform three services for her, is an agreement that she won't use her powers against him for refusing to accept. She promptly uses her powers to put Harry in a lot of pain — but not to extort his cooperation, but just because she likes doing so.
While being hunted by the gruffs, Harry considers cashing in his boon from Summer to protect him. He reconsiders when he realizes that they could "protect" him by severely injuring him badly enough to take him off-mission so the gruffs no longer considered him a threat.
When Harry meets the Elder Gruff, who actually likes Harry but is Just Following Orders, he has already "won" but discovers that the gruff is still required to try to kill him as long as they are both on the field of battle. He cashes in his boon for a doughnut. And not a magicked doughnut, but a fresh one. With sprinkles., which forces the hit man to leave the island, and gives Harry time to do the same.
At Harry's birthday party in Cold Days, one of Mab's rules is that no blood may be spilled. It turns out there are plenty of ways to kill someone without spilling blood, all of them perfectly acceptable.
Harry himself is a fan of loophole abuse:
When he accidentally lands in the Erlking's domain, the goblin sarcastically refers to Harry as his "guest" so Harry seizes upon that, claiming the protections of a guest.
In Ghost Story, he's told only crazy ghosts can become corporeal and interact with the real world, and quickly realizes that the actions he takes, the things he does, marks him as more than slightly unhinged. Welcome to the real world, ghost Harry!
On the other hand, he also knows when he's outmatched in the loophole-fu department: when he agrees to become Mab's Winter Knight he doesn't even try to weasel his way out of it using Sidhe logic, because he knows he'd fail. Instead he hires Kincaid to kill him the next morning, then has Molly erase his memory of doing so.
In Skin Game, Michael (a crippled and retired Knight of the Cross) promises Nicodemus (a very dangerous host to a very dangerous Fallen Angel) that he will step outside his house's protective barrier in exchange for his friends' safety. Michael is a good enough man that the Archangel Uriel himself comes down to try and get him to stop. Unfortunately, angels can't interfere with free will, so he can't actually prevent him from leaving. And due to the Balance Between Good and Evil, Uriel can't heal Michael, since that would give an opportunity for an equally powerful demon to act as well. Uriel then chooses to exercise his own free will by loaning Michael his Grace, his angelic power, essentially turning him into an archangel for a moment—with the happy side effect of curing all his wounds for as long as the power is within him. Since Uriel can destroy galaxies with a thought, Harry compares this to loaning someone a jumbo jet because he really needed a reading light. And if Michael does anything he shouldn't with the power, Uriel will Fall, and they'll have a second Lucifer on their hands. On a related note, Michael promised Nicodemus he'd step outside his house's protective barrier. He never promised to surrender.
In the Dale Brown novel Flight of the Old Dog, the Soviets refuse to shut down their Kavaznya laserCannon, claiming that the previous strategic arms treaties said nothing about ground-based laser systems. In Shadows of Steel it is said that while the USSR and China signed arms control treaties against selling to Iran, none of the other post-Soviet states did.
In The Guardians, there ain't no rule that a Guardian can't become human, exercise human rights, and become a Guardian again. And they gain a second Gift upon their second self-sacrifice, which is why Michael has so many Gifts.
The land of Xanth has a law stating that the king must be an adult Magician and forbidding ruling queens. However, in one book an enemy is incapacitating kings one after another and they're running out of Magicians... until one of the heroes decides that if a Sorceress is really just a female Magician, there's no rule that they can't have a female king.
Count Olaf of A Series of Unfortunate Events plans to marry his ward Violet to get at her inheritance. (And, it is strongly implied, some other things.) She's underage, so the marriage has to be approved by her parent or guardian. In this case, that would be Count Olaf. He stages the marriage in the guise of a play about a wedding, even tricking a judge into performing the ceremony, with the audience as witnesses. Violet takes advantage of a loophole herself; the law states she has to sign the marriage license in "her own hand". She's right-handed, so she simply uses her left hand, making the marriage null and void.
The film version plays out slightly differently. Olaf caught the kids reading law books earlier in the film, and thus catches Violet's trick. After the contract is signed, he gloats about it. When Poe demands Olaf be arrested, the Baliff says, awkwardly, that the wedding was perfectly legal. Then Klaus uses the same device Olaf used to kill the Baudelaire parents to set the contract on fire. The audience then arrests Olaf.
In her Tales of the Five Hundred Kingdoms novel Fortune's Fool, Mercedes Lackey uses an ifrit as the villain. At the end, the ifrit is bound into his bottle. But the bottle cannot be sealed permanently; there must be a release condition, and it must be possible, however unlikely. So the ifrit is bound into the bottle "until you repent and reform and join the ranks of the Lawful Jinn of the City of Brass!" Geniekind have free will, he can choose between good and evil.
The classic example of a loophole in fantasy fiction has to be in The Lord of the Rings. The elf Glorfindel restrains a hot-blooded human king from pursuing the Witch-King, counseling him "Far off yet is his doom, and not by the hand of Man shall he fall." Two thousand years later, the now Lord of the Nazgul is on the Pelennor battlefield, reminding a lowly warrior of Rohan of this destiny. Dernhelm then takes off "his" helmet and shakes out her hair and announces herself as female. Assisted by a Hobbit who has passed under the radar, she downs the Witch-King...
In the novel Citadel, a junior welder places a fake spider in the work sled of a hated coworker shortly before he goes out on EVA. When questioned about it, it is pointed out that there are regulations about tampering with a coworker's spacesuit, but not about the sleds. It is strongly implied that the safety regulations in question are rewritten after that incident.
A children's picture book actually has this as a plot point. A child is playing outside this apartment complex, and loses a toy to the other side of the road. (Either a plane or a ball) Since he had been forbidden to cross the street by himself, he tries to ask passing adults to escort him across the street but nobody does anything. Finally, he decides to climb up some objects such as a tree, then his weight causes the top of the tree to lean, allowing him to grab the tree on the other side of the road, where he picked up his toy and threw it back across the street, and repeated the process to get back across. His reasoning for doing this was because he didn't actually set foot on the street, and he was forbidden from walking across the street without an escort - his mother had not told him he couldn't find another creative way across.
In the novel Vampire High, a group of vampire students decide to join the water-polo team and take their school to its first-ever victory...and then it turns out that these students have a strange and rare gene that lets them become seal-human hybrids when in the water. With their enhanced strength and speed, they win the game by a two-hundred point margin, and a group of lawyers present protest, saying that the rules state only a human can play on the team. The protagonist's father tells them that "The law hasn't quite decided what is and is not human," and points out that there were other vampires on the team who didn't have the gene, and no one had complained. The lawyers persist, however, until the protagonist's father tells them he's a lawyer in a VERY powerful and influential firm, and the guys back off.
The Pevensies justify wearing fur coats that don't belong to them on their foray into another, wintery world, on the grounds that they won't even be taking them out of the wardrobe.
King Aslan pulls this off in a plan against the White Witch. According to the rules of the Deep Magic, Edmund must be killed on The Stone Table because he was a traitor. Aslan then offers to go in his stead and die. Turns out he was banking on the rules of the Deeper Magic, a rule that Jandis didn't know of, to bail him out: if someone who is innocent is sacrificed on The Stone Table, then that person is revived. Guess who Aslan is.
In the Clockpunk fantasy Goblin Moon, a friend of the heroine's aunt marries a criminal she's never met, just before he is executed for his crimes. She does this because she owes her creditors a fortune, which automatically become her husband's problem as soon as she weds him; as an instant widow, she's free of her debts and can go on to marry the man she actually loves. All the criminal gets out of it is the company of a prostitute and a bottle of wine for his last night, courtesy of a well-bribed jailer.
In the first Red Dwarf Book, Infinity Welcomes Careful Drivers, it is explained that after the advent of genetic modification, specially created athletes were designed for their league games with their entire bodies suited for their role - twelve foot basketball players, boxers with heads of unthinking muscle and so on. One football (soccer) team fielded a goalie which was a massive oblong block of flesh that filled the goal mouth. Somehow they still failed to qualify for the second round.
The alien frogs in Tom Holt's Falling Sideways have a very clear rule about Thou Shalt Not Kill. They do not have a very clear rule about Thou Shalt Not Make People Believe Themselves To Be Frogs And Therefore Starve To Death On An Unsuitable Diet.
According to Captain Bartleby in 1636: The Saxon Uprising, there's no rule that the Dollar is the exclusive currency of the USE, allowing the Third Division the capability to produce its own currency for purchasing supplies.
In Animorphs, to prevent the destruction of the galaxy that will be inevitable should they come to direct blows, the Ellimist and the Crayak set a bunch of rules for themselves in how to resolve their conflict... and then find as many loopholes as they possibly can. The Ellimist isn't allowed to directly save all humans from the Yeerks, but can take a small sampling of them and relocate them on another planet? Show the world's anti-Yeerk heroes a possible future to encourage them to agree to relocation... but give them a massive hint for how they can score a decisive victory over the Yeerks in the process. The Crayak's lackey, the Drode, isn't allowed to kill any sentient life? Set the self-destruct sequence on a bunch of robots (robots aren't alive!) to draw his targets into a situation likely (but not guaranteed) to kill them.
In a Berenstein Bears novel, the new principal puts in a school dress code. They proceed to piss him off on the very first day it's in effect by doing just this. Among these are wearing green jeans instead of blue jeans, and wearing a Batman cape instead of a Superman cape.
In the Safehold series by David Weber, the heroes relentlessly exploit loopholes and creative interpretations of the religious prohibitions concerning technological advances.
One of the more notable examples of outright abuse comes with explosives and chemistry: the "archangels" who created the rules couldn't explain why certain things shouldn't be done (since that would expose people to too much knowledge), only saying that mixing chemicals X and Y would result in dangerous, magical retribution. If, however, you wanted that "magical retribution" to occur in certain controlled conditions, say in a fuse attached to a gunpowder-filled artillery shell...
Gets even better when one of the people directly responsible for enforcing the restrictions gets brought in on the secret (namely that the religion in question is a Path of Inspiration) and starts helping the heroes abuse loopholes. Naturally having shot down attempts at loophole abuse in the past, he's well familiar with how that game is played.
In Fate/Zero, Kiritsugu signs a Magically Binding Contract with Lord El-Melloi - El-Melloi will order Lancer to commit suicide and withdraw from the Holy Grail War, and in exchange Kiritsugu cannot harm him or his fiance Sola-Ui (whom Kiritsugu is holding hostage). As soon as Lancer is dead, Kiritsugu's partner Maiya guns down both Sola-Ui and El-Melloi.
This is highly ironic, because Lord El-Melloi did use this trope as well. He had already modified and exploited the contract system so that, while he carried the Command Seals, Sola-Ui was the one supplying Lancer with the prana he needed. This allowed El-Melloi to fight at full strength without needing to worry about sharing his prana between himself and his Servant.
Kiritsugu again: Ain't No Rule that the Einzbern Master has to be an Einzbern, or that a Master has to be the one who supports his Servant.
The Black Knight's swordplay is so practiced that he can perform even his most advanced techniques instinctually, represented by the "Eternal Arms Mastership" ability. This allows him to ignore the mental restrictions of his Berserker class completely, while keeping the improved stats.
Isaac Asimov: The Robot stories are a study in Loophole Abuse. Robots must obey the Three Laws, but many of the stories place a Robot in a situation where strict adherence to the Three Laws is impossible, and so the Robot must engage in some judicious moral wrangling to reach a resolution. Sometimes it boils down to a "spirit of the law" versus "letter of the law" situation. Other times it involves situational interpretation of the Laws (i.e., a Robot cannot harm a human, but what constitutes "harm?" Does social embarrassment count as "harm?" etc.) Chronologically later stories involve the creation of a "Zeroth Law," and introduces the concept of the "Greater Good" into the Robots' morality.
As an example, Susan Calvin gets called to find a missing robot in a space base, because it had been told to "get lost", and it joined a recently come group of physically identical robots. Susan tried to weed the lost robot out by simulating a human getting crushed under a weight, because she knew the First Law ("A robot may not injure a human being or, through inaction, allow a human being to come to harm") had not been fully implemented (becoming "A robot may not injure a human being"), but they all jumped. The next experiment she conducted, a similar test but placing something between the robots and the human that would have killed them, none of the robots moved. When she asked the robots about the incident, they stated that one of them had convinced the others that uselessly sacrificing their lives for one human would mean none of them would be around to protect any humans later.
In John C. Wright's Count To A Trillion, Menelaus tries a nutty, very hypothetical, and dangerous experiment as soon as the shuttle leaves Earth — meaning he's no longer covered by Earth law, and not yet under the captain's authority on the ship. Reaction to this reasoning: they knew they shouldn't have brought along a lawyer.
In A Song of Ice and Fire, the laws of hospitality are sacred in Westeros. Not so much any other laws; when the legendary Rat Cook served a king his own sons in pies, there was no problem with the murder and cannibalism parts; he was condemned (and cursed) only because they were his guests. But when Lord Wyman Manderly desired to take Revenge with a capital R on the Freys (and Boltons), and decided to emulate the Rat Cook, he carefully waited until his Frey guests were leaving, gave them gifts which formally marked their departure, and then had them murdered, made into pies, transported to a feast hosted by the Freys and Boltons, and served up. He ate several slices himself, with relish.
Similarly, the Dothraki have a holy city Vaes Dothrak. No Dothraki may wear a blade or shed a free man's blood in the city. Supposedly, some khals employ men to strangle people with silk, which doesn't shed blood. Viserys wears a sword, claiming that since he isn't a Dothraki (though this may not actually apply). Khal Drogo then kills him by pouring molten gold on him, which again doesn't spill his blood.
While it never goes off, Arianne Martell's scheme to crown Myrcella has this as one of the legal excuses — by Westerosi law, females are placed far back in the line of succession — but when Dorne joined the Iron Throne, part of the agreement was that in Dorne Dornish law applies, and Dornish law does not care about gender when it comes to succession.
Callahan's Bar has a very strict rule against asking prying questions of someone who doesn't want to talk, enforced by the piano player's blackjack.
As a card-carrying Sophist, I will now proceed to make some prying statements, and if you choose to react to any of them it won't be my place to stop you.
In The Acts of Caine, a human surgically altered to look like an elf meets the exiled elf prince, who has been trapped in a human brothel for centuries and just wants to go home. The human, with his rather obsessive knowledge of elven court customs, finds a way to get around the exile: If the human meets with the elven king and presents the exiled prince as a gift, the king will be forced to take his son back and treat him well. When they try this trick, however, they find out that the elf king had long since rescinded the exile, having deeply regretted sending his son away, and welcomed him back with open arms. What's more, the human was adopted into the royal family for bringing the prince back.
Gods and Generals has a couple of instances. Joshua Lawrence Chamberlain is given a two-year sabbatical in hopes that he'll go to Europe and get the war out of his head—instead he goes to the governor of Maine and gets a commission as lieutenant-colonel of the 20th Maine. In a separate incident, General Hancock is repeatedly ordered to retreat despite being in an excellent position to flank the enemy. When he's given a final warning by the messenger, Hancock makes his troops "withdraw" into the Confederates.
In The Tamuli, it turns out that the situation with the Delphae is this. They're cursed, all right... but the local rules of magic don't actually specify that there has to be a real downside to the effects of a curse. Since enchantments reveal their presence to anyone with magic, while curses are so quiet as to dampen the 'sound' of any magic done in connection with them, being 'cursed' serves the Delphae, who want to hide from the rest of humanity, well.
In The Unexpected Enlightenment of Rachel Griffin, Rachel and her cohorts have a pressing need to get to the infirmary; but, students are not allowed out of their dorms after curfew. There is no rule that says you can't put yourself in the infirmary by having your friends punch you repeatedly.
In the Rainbow Magic series, the second series published, the Weather Fairies, has this. Jack Frost promised not to harm the Rainbow Fairies at the end of their series... so he harmed the Weather Fairies instead.
Richard Marcinko of the Rogue Warrior novels claims to really have recovered stolen nukes, and saved London from a biological attack, and take down a Presidential candidate, stopped Russian and Chinese hard liners, ect. But the Navy won't let him write those exploits so he writes the stories as fiction.