History Main / NewRulesAsThePlotDemands

* ''Franchise/AceAttorney'' introduces new laws relatively frequently, almost without exception to inconvenience the defense. The most egregious example of this happens during the final case of ''VisualNovel/SpiritOfJustice'', [[spoiler:the prosecutor of which being the monarch of the country the trial is being held, and who has no problems literally rewriting the law on the spot. Of course, she's also the culprit of both crimes you're going to court for, so she has a vested interest in winning the trial at all cost.]] In fact, the only way to win that case is to [[spoiler:make sure that these new rules are unenforceable by turning the royal guard against the prosecution.]]

* It should be noted that most of the examples in this section are based off of earlier parts of the series, when the rules for an actual physical card game had either not been created or were still in their infancy, as the manga was first published in 1996 while the first set of trading cards weren't released until 1999. Basically, the games, cards, and interactions were treated more like {{Shonen}} fight scenes than an actual card game with defined rules. Cards were allowed to have creative or bizarre interactions resulting in complex cause and effects that often had some degree of logic behind them, but would never exist in a real card game. While some stranger interactions were eventually implemented in one way or another, many one off interactions are simply ignored for the rest of the series and in the game. The switch between manga and anime doesn't help, as it means that a lot of already dodgy interactions were changed due to differing rulesets.

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** Ghost-type Pokémon are generally portrayed as having the [[ElementalRockPaperScissors advantage]] over Psychic types ...outside of a single episode of the Johto arc, where is portrayed as having a ''dis''advantage instead.

* During Fukuwara Mask's town revitalization wrestling event in ''Anime/TigerMaskW'', the count-out rule was not enforced for the final match because the mayor asked the referee not to.

** Solar Beam is a ChargeAttack, but sometimes certain Pokémon just fire it immediately without charging and with no Sunny Day to accelerate the process. This is especially blatant in the Kalos Saga.

* ''VideoGame/CommandAndConquerTiberianDawn'': GDI mission 12, you are tasked with rescuing dr. Mobius from a damaged base that is under siege by Nod forces. When the game starts your small land force reaches the damaged base and a transport helicopter comes in... only to be shot down by 4 SAM sites beyond the river right north of the base. Your mission then becomes using whatever you can deploy to destroy all SAM sites and clear the landing zone for a new helicopter for Mobius. You might think that destroying those 4 missile launchers would be enough (even if technically there is room for landing on the southern edge of the map...). Instead, you have to go finding all SAM sites in the map until the northern border, where their range can't reach your base. It is never pointed out why SimpleSolutionWontWork. In real life, this could be explained by the fact that SAM sites have a range that is much larger than that in-game, but the gameplay always used a different limit that is still effective in this mission yet won't allow you to land safely an helicopter for the purpose of the objectives.

[[folder:Tabletop Games]]
* Most tabletop roleplaying games incorporate what's generally known as "Rule 0", which is [[ScrewTheRulesIMakeThem the GM's word is law,]] giving him free rein to adjust or ignore the rulebook at his whim as well as simply make up new rules on the spot. It's to be hoped that the GM will only do this to make the game more fun. HouseRules should generally be negotiated and agreed upon before play begins.
* Similar to Rule 0, mentioned above, RuleOfCool is often invoked in less serious campaigns (or even more serious ones, if the said thing is ''really cool''). While this is sort of a subversion Rule 0 (breaking the rules as the PLAYERS' plot demands it, not the GM's), being that most tabletop {{Role Playing Game}}s are considered collaborative storytelling, it still applies.
* When players have rule disputes in wargames, best solution is usually to simply roll a die, then check the FAQ for a ruling sometime later. Players often like adding story-based rules to the games, too.
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** Then there are Silver-Bordered cards (as opposed to normal Black Border cards), which intentionally turn this up even further. All Silver-Bordered cards are explicitly not legal in any sort of formal play and don't exist on any digital clients of the game. They allow mechanics that don't actually work within the games normal rules, having cards that are both in your hand and in play, having non-integer stats (including fractions, infinity, and π), influencing games outside of the one they're cast in, and getting benefits from high-fives from people outside the game. Silver-Bordered cards exist primarily for joke sets and promotional cards, but some of the more feasible designs have inspired regular black-bordered cards, like Giant Fan inspiring Power Conduit and The Cheese Stands Alone being reprinted verbatim as the black-bordered Barren Glory. Some also are simply regular cards but with their effects turned UpToEleven, like having Triple-strike to top the Black Border double-strike.

* Mercilessly parodied in ''WebVideo/YuGiOhTheAbridgedSeries'' by exaggerating the trope as it was played in the source material UpToEleven. In fact, it's strongly implied ''nobody'' has ever played the game properly: the rules are apparently so overly complicated and impossible to understand, Duelists don't even bother reading them and just make up what they can do on the spot as their duels go on. When Kaiba announces the Battle City Tournament will actually follow the game's official rules, this is considered as the first real twist of the show by the other characters.

** The second time is even weirder when you fight [[CopyCatSue Llednar,]] who is actually invincible.[[spoiler:Cid says Llednar's Omega spell is too dangerous to use, and throws an advanced law at him to prevent him from using it. Except it doesn't prevent anything, after a short time Llednar will start to cast the spell, but Cid sends him to jail before he finishes it. Technically speaking, Llednar never managed to break the law since he was sent to jail before that, but thanks to that, you can win the battle.]]

[[folder:Real Life]]
* Carnies have a term called an ''alibi'', which is when someone who has apparently won a game of chance is told about a previously undisclosed rule, in order to be able to deny giving them a prize. A common example is stating that the player crossed an invisible "foul line". At least most of them are up front about not allowing underhand shots.
* The UsefulNotes/{{N|ationalFootballLeague}}FL has some rules that are so obscure that even coaches are not generally aware of them. Sometimes they are called attention to in playoff games, which leads to accusations that the league is manipulating the outcome to allow the more popular team to advance to the UsefulNotes/SuperBowl. Infamous examples include the [[http://en.wikipedia.org/wiki/Tuck_rule tuck rule,]] which changed the outcome of the [[http://en.wikipedia.org/wiki/Tuck_rule_game 2002 [=AFC=] Divisional Playoff Game,]] and the [[http://en.wikipedia.org/wiki/Bert_Emanuel "Bert Emanuel"]] rule, so named when the Tampa Bay Buccaneers had an apparent pass reception overturned by officials in the [[http://en.wikipedia.org/wiki/1999–2000_NFL_playoffs#NFC_Championship:_St._Louis_Rams_11.2C_Tampa_Bay_Buccaneers_6 2000 [=NFC=] Divisional Championship Game.]] The latter ensured that the "Greatest Show on Turf" offense of the St. Louis Rams, considered to be more ratings-friendly than the Buccaneers' stifling defense, would reach the championship, while the former extended the chances of the New England Patriots and Tom Brady's star power. A non-playoff example occurred during a 2010 game between the Detroit Lions and Chicago Bears, in which a potentially game-winning touchdown catch was overturned when officials ruled that Lions receiver Calvin Johnson failed to maintain control of the ball because [[http://www.huffingtonpost.com/2010/09/12/calvin-johnson-touchdown-_n_713897.html he set it down too quickly after catching it.]]
** The problem with the NFL is the amount of nitpicky rules that the human refs are supposed to take into account along with the general vagueness of a lot of rules coupled with the limitations of the review system. For many years, the official NFL rule book was not available on the internet ([[http://www.nfl.com/rulebook now it is,]] along with the offical casebook), and most people aren't privy to NFL officials meetings that clarify interpretations of the rules. Most of the examples would definitely be subjective for these reasons (they may appear to be bad calls to people on the losing end or 50% of non-vested viewers while the other half will feel otherwise). An example: during a punt, the ball was rolling into the end-zone and a player from the punting team dove onto the ball, initiated contact with the ball outside of the end-zone and released contact with the ball after it was in the end-zone. It was ruled a touchback, it was challenged, reviewed and upheld. The rule that allows you to down the ball is called illegal-touching and doesn't clarify (at least in the internet rules version) whether you just have to touch the ball or have to possess the ball for it to be downed. It's interesting because for it to be considered a fumble or a muffed reception, the receiving team merely needs to graze the ball. Interpretations of the rules seem to follow along the US Justice system whereby previous interpretations continue until corrected by a higher authority.
** Illegal touching means that the ball is downed when the kicking team gains control of it and cannot be downed in such a way as to give the receiving team worse field position than when the kicking team first touched the ball. Thus, if a member of the kicking team attempts to down the ball, but it goes into the endzone off his hands, it's a touchback. If the ball is deflected toward the receiving team's endzone and then downed, the ball is placed back where it was first touched. And now for the GameBreaker: if a ball is touched by a member of the kicking team and a member of the receiving team then gains control before the kicking team does, the ball can be advanced by the receiving team, the receiving team CANNOT FUMBLE. If the kicking team recovers a fumble or intercepts a lateral pass on such a play, the ball is downed instead of going back to the kicking team. This means that, except for the risk of throwing the ball back through your own endzone for a safety, there is no risk to attempting a rugby-style multi-lateral pass play (which, like pulling the goalie in ice hockey, is normally reserved for an end-game desperation play, but is a free option on a delayed penalty, wherein the opposing team is not allowed to gain possession).
** If a hit or tackle causes a major injury too many times, the NFL may declare it illegal, so players best keep abreast of what tackling techniques are allowed and which are not if they want to avoid fines.
* UsefulNotes/{{NASCAR}} has been known to change the rulebook on the fly as needed. Sometimes it seems arbitrary, sometimes it's in response to apparent overdominance, and sometimes it's just figuring out that having people race at full speed to the start/finish line when a caution comes out is less than safe when the reason for the caution flag is a guy sitting helpless a few hundred metres in front of said start/finish line, as such an incident happened with Dale Jarrett in Loudon in 2003.
* Similarly, the [[UsefulNotes/FormulaOne Formula 1]] rules on pit stops, tyre management and Safety Car scenarios (just to name the most usual ones) seem to change every year, if not every few months.
* As society is constantly changing, the law needs to be constantly revised, resulting in constant new laws introduced, and changes to original laws. Due to the obvious potential for abuse, many countries have a law banning or restricting ''ex post facto'' laws (also known as a Grandfather Clause), which makes laws unable to be applied retroactively (in other words, you can't prosecute someone if whatever they did was legal at the time). In some countries, new prohibitions cannot be retroactive, but ''repealing'' a prohibition is (in other words, if something becomes legal, the perpetrators are released from jail).
* The codes for buildings, electricians, plumbers, etc., are ''constantly'' being revised and changed to meet with new technology or to address things that were later realized to be not restrictive enough or ''too'' restrictive. Keeping up with these code changes is a major part of these peoples' jobs. Like above, there is also a Grandfather Clause which states an installation that was up to code upon installation is ''still'' up to code even if such a thing would be prohibited nowadays, unless of course it is so blatantly dangerous that it is an active hazard (knob and tube wiring, lead piping for potable water, and asbestos being three major examples of things that ''must'' be removed upon discovery).
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** Riding Duels are duels on motorcycles. They have some special rules and special Spell Cards, the Speed Spells. However, Yusei, Jack and Crow team up together to duel Rex Goodwin. The twist? They duel on their motorcycles, but Rex Goodwin [[IHaveTheHighGround has just the high ground]] and stands there the whole time. There is no mentioned rule of semi-Riding Duels being possible. Like his three opponents, Goodwin is limited to use Speed Spells and he gets Speed Counters, which can increase or decrease the speed of the D-Wheel, but he has no D-Wheel. Later, he even says that Crow and Jack don't get any turns as long as they cannot drive their D-Wheels after they crashed ([[ScrewTheRulesIHaveSupernaturalPowers and they crashed because he sabotaged them in the middle of duel]]), but he still isn't riding a D-Wheel, yet he is excluded from the rule.

* An episode of the live-action kids drama ''Series/{{Zoey 101}}'' had a ''Series/BattleBots''-style remote-controlled robot war, where the main characters lose to the [[HollywoodNerd stereotypical nerds]] after their bot destroys the other with a hammer. When the main character's best friend comes in with her own tiny bot, the nerds laugh at it until it fires a huge ''laser'' at the other bot, completely destroying it and winning the match. Apparently, there [[LoopholeAbuse Ain't No Rule]] saying you can't use military lasers in the competition.

** During the Pegasus duel, it seems like nobody involved knew how Toon Monsters worked, having them be Normal Summoned through Ultimate Offering and getting their levels reduced via Cost Down to reduce Tribute requirements--neither of these are true in the real game, where Toons can only be Special Summoned and have an explicit number of monsters that need to be Tributed to play them. Curiously, their "summoning sickness" (being unable to attack on the turn they're summoned) is kept intact, and it's also correctly ignored for Toon Dark Magician Girl (who doesn't suffer from it in the real game).

* In the first season, Duel Monsters was played on a large field with multiple areas of attack. Different monsters had different field advantages depending on where they were played and it was never possible to keep track of with the limited information given. The bonus was usually 30%, though.

Also compare HowUnscientific, NewPowersAsThePlotDemands, GameplayAndStorySegregation, ScrewTheRulesIMakeThem, and LoopholeAbuse. GoldenSnitch is a subtrope. Be sure to stop by SeriousBusiness on your way out.

* In the same episode as the above, the flying castle itself has the effect of hiding the villain's monsters in darkness, so Yugi can only attack the darkness and get his monsters killed by cards he can't see. How exactly is that supposed to work ''without'' holographic technology? 'You're attacking my monster? Sorry, it has higher ATK than yours. No, I can't prove it, that would defeat the whole purpose of the shrouding darkness. Just take my word for it, will you?' (Most guesses have assumed it'd work by flipping the cards facedown, at which they'd only be revealed when attacking, which does briefly happen at one point.)

* In ''Manga/DragonBall'', this is how the rules of the wish-granting dragon Shenlong were constructed [[WritingByTheSeatOfYourPants as the story went along.]] At first Shenlong could grant any wish, no questions asked. This holds true until the Saiyan Arc, where it's introduced that he cannot restore someone back from the dead more than once (in addition to a similar rule where he can't grant the same wish twice), to add permanence to the later death of Chiaotzu. In the same arc, he also reveals that he cannot kill the oncoming villains as they exceed his power[[note]][[FridgeLogic Why they didn't ask to blow up their space pods instead is anybody's guess.]][[/note]]. In the Namek Arc, it's introduced that he cannot revive anybody who died of old age, [[RuleOfDrama just so that King Kai has to bank on the Grand Elder, the one he wanted to revive, on having died due to the added stress of Frieza exterminating his people.]] And at some point, it's established that he cannot revive anyone who died over a year ago - [[Anime/DragonBallZResurrectionF except no,]] he totally ''can'', but doing so returns the subject in the [[HalfTheManHeUsedToBe exact]] [[LudicrousGibs physical]] [[AndIMustScream state]] they were in at the moment of their death, rather than in full health.[[note]]It's worth noting that ''Anime/DragonBallGT'' introduced the Black Star Dragon Balls that operated under the original "any wish" pitch, with the downside that it would cause the planet the wish was asked on to blow up in a year if the Balls weren't collected from across the galaxy and returned).[[/note]]

** Later, Yugi attacks it once its ATK was low enough for his weaker monsters to defeat it. However, it is stated that because Blue-Eyes Ultimate Dragon is a Fusion Monster that requires three Fusion Material Monsters, it must be attacked three times to completely destroy it, so Yugi's attack killed only one head. And then, Kaiba uses Monster Reborn to revive the destroyed head, returning it to the power level of a regular Blue-Eyes White Dragon. No other Fusion Monsters ever display this characteristic and this is never brought up again; it's ''possible'' this might be a trait of Blue-Eyes Ultimate Dragon, in which case the trick would work in the rules (fused materials go to the Graveyard, so Kaiba was effectively just reviving one of his regular Blue-Eyes), but the the new head is treated as incorporated into Ultimate Dragon.

* [[SocietyMarchesOn As society is constantly changing,]] the law needs to be constantly revised, resulting in constant new laws introduced, and changes to original laws. Due to the obvious potential for abuse, many countries have a law banning or restricting ''ex post facto'' laws (also known as a Grandfather Clause), which makes laws unable to be applied retroactively (in other words, you can't prosecute someone if whatever they did was legal at the time). In some countries, new prohibitions cannot be retroactive, but ''repealing'' a prohibition is (in other words, if something becomes legal, the perpetrators are released from jail).

* It should be noted that most of the examples in this section are based off of earlier parts of the series, when the rules for an actual physical card game had either not been created or were still in their infancy, as the manga was first published in 1996 while the first set of trading cards weren't released until 1999. Basically, the games, cards, and interactions were treated more like {{Shonen}} fight scenes than an actual card game with defined rules. Cards were allowed to have creative or bizarre interactions resulting in complex cause and effects that often had some degree of logic behind them, but would never exist in a real card game. While some stranger interactions were eventually implemented in one way or another, many one off interactions are simply ignored for the rest of the series and in the game.

* This trope is relatively justified when more than two duelists participate in a duel. The game had no 2v2 rules for some time, and there are still no written rules for anything other than 1v1 and 2v2. The solution is basically just to come up with a set of rules everyone agrees to which happens a few times in the series to allow for things like 4-player free for all. What's more, the actual mechanics are known to change from appearance to appearance. Sometimes, players can use cards controlled by an ally player as if they control them (for instance, fusing them or benefitting from protection effects), and sometimes they're treated as an opponent you're incidentally not attacking right now (for instance, attacking them). Sometimes, allied players share Life Points, other times, they have separate counters. It's particularly strange in cases of asymmetric teams, such as a two-on-one duel. In particular, whether or not the solo player gets extra turns or greater starting LP varies.[[note]]For instance, if Player 1 and 2 are on one side and Player 3 is on the other, does the turn order go 1>3>2>3>repeat, or 1>2>3>repeat?[[/note]] A later example is the Duel with Doctor Faker in ''Anime/YuGiOhZEXAL'', which is a three-on-one duel; he gets triple starting LP, but his opponents share a single regular-sized LP counter. This might be to compensate for him getting a third as many turns, but it's still nothing like how tag duels have worked before or since.

* The Battle City rules themselves count as this. The rules used in the show were deliberately moved closer to that of the real life TCG with no greater justification than "Kaiba changed the rules for his tournament". If the new rules had just been for Battle City, it would be one thing, since tournaments sometimes use HouseRules, but Kaiba somehow makes the rule change ''permanent'': even after the tournament is over, nobody ever goes back to the pre-Battle City rules despite these being the official ones in-universe. Even players from alternate universes use Kaiba’s new rules for some reason! Out-of-universe, this was due to the "Expert Rules" format being introduced to the real card game (in its first few months in Japan, the card game used a Duelist Kingdom-esque ruleset), which was initially introduced as an alternate format but quickly became the only one.
* Each time The Winged Dragon of Ra is played it has a new power. First, there is that special writing which can only be seen under the light of the God (and that means the hologram). When Mai summons it, it doesn't work, since you need to read the text (that is written in Ancient Egyptian) to activate it. Marik promptly reads the text, taking Ra to his side of the field and activating it. Next battle, it has two new abilities: it can increase/decrease its ATK by decreasing/increasing his owner Life Points at the owner's will, and it can attack at the same turn as it has been summoned. And against Jonouchi, Ra has a Phoenix Mode that allows Marik to destroy all monsters of the opponent at the cost of 1000 LP, and it cannot be harmed in this mode. And this is all before the battle against Yugi, when it shows its real power.

* During the life-threatening duel between Yugi and Jonouchi, where the winner gets the key to free himself from the anchor, Yugi chooses himself as Jonouchi's Spell Card's target. Yugi lose all of his Life Points, but Jonouchi realizes that his Spell Card allows him to be attacked by Yugi's Red-Eyes Black Dragon, so Jonouchi would lose all of his Life Points as well. Regardless how you look, Yugi lost his Life Points first, and Jonouchi needs minutes to figure out that he himself can be attacked. Both effects of his Spell Card do not work simultaneously.

* In Anzu/Téa's duel against Otaki/Crump, Anzu activates a Spell card that summons a Dark Magician to the field. But she didn't have Dark Magician in her deck, so she just magically steals it from Yugi's deck, who was merely watching at the time.
* Another aversion, a similar case like the Toon Monsters above, Yugi first believed that Noa/Noah is violating the rules when he introduces Spirit Monsters. Noa explains that the Spirit Monsters are legal cards that are secretly created by Pegasus, but since nobody has ever heard of them, they are a completely new type of Monster Cards in this game.

* In ''Manga/YuGiOhR'', there was an odd rule pertaining to Fusion Monsters: a duelist's field was considered to contain both the Fusion Monster and its components. This meant Yugi's Arcana Knight Joker counted as ''four'' monsters when determining the ATK of Devil's Eraser, which had 1,000 ATK times the number of opposing monsters. The rule was implemented simply to make it strong enough to defeat Arcana Knight Joker.

** While in the English dub, Anubis tenfolds Theinen the Great Sphinx's ATK with [[ScrewTheRulesIHaveSupernaturalPowers magical powers,]] in the Japanese dub, Anubis activates Theinen's (anime) effect. Theinen gains the ATK of all monsters that are in the graveyard, a total amount of 31,500 ATK.[[note]]3x Blue-Eyes White Dragon (3x3000), Blue-Eyes Ultimate Dragon (4500), Blue-Eyes Shining Dragon (3000), Familiar Knight (1200), Rare Metal Dragon (2400), Des Feral Imp (1600), Paladin of White Dragon (1900), Peten the Dark Clown (500, two of the three are banished), Spear Dragon (1900), Andro Sphinx (3000) and Sphinx Teleia (2500).[[/note]]

* It should be noted that most of the examples in this section are based off of earlier parts of the series, when the rules for an actual physical card game had either not been created or were still in their infancy, as manga was first published in 1997 while the first set of trading cards weren't released until 1999. Basically, the games, cards, and interactions were treated more like {{Shonen}} fight scenes than an actual card game with defined rules. Cards were allowed to have creative or bizarre interactions resulting in complex cause and effects that often had some degree of logic behind them, but would never exist in a real card game. While some stranger interactions were eventually implemented in one way or another, many one off interactions are simply ignored for the rest of the series and in the game.

** Especially frustrating is the league's apparent knee-jerk reaction to any hit/tackle that causes a major injury to a few players by declaring it illegal, leading to players getting massive fines/suspensions for hits that many observers claim was "just a good football play" and those observers complaining that the game is becoming sissified.

* In ''Film/TheCannonballRun'', they make a point at beginning of each team punching a card in a time clock to note their start time and the cars left at staggered intervals. This indicates that the winner would be the team with the best overall time, not necessarily who makes it to the finish first. At the end, all the racers act like it's the first team to punch their ticket that wins and JJ is made a Victor for stopping to save a dog, despite the fact they left quite a bit after the "winner". Everyone else just gives up.

* In his duel with Kajiki/[[DubNameChange Mako,]] Yugi calls an attack on "Full Moon". Three major problems with that. First, "Full Moon" is Yugi's own card and is on his side of the battlefield. Second, it's a magic card, not a monster. Third, he's trying to ''stab the moon with a sword''. Yet not only does this somehow work, it dramatically alters the battlefield, causing the tide on the battlefield to go out [[FridgeLogic lower than it was before he summoned the Moon,]] and ''beaching Kajiki's sea monsters''. Konami is well aware of how ridiculous that is, as evidenced by this card: [[https://yugipedia.com/wiki/Attack_the_Moon! Attack the Moon!]] (Even then, that card only lets you destroy your ''opponent's'' spells, not your own, though you could achieve similar results to what Yugi did by destroying your opponent's field spell with it.)

* In the first season, Duel Monsters was played on a large field with multiple areas of attack. Different monsters had different field advantages depending on where they were played and it was never possible to keep track of with the limited information given. Often, the bonus would vary wildly from doubling a monster's stats to tripling them to raising them by 50%. Duelist Kingdom standardized it to 30%, resulting in weird things like the Player Killer of Darkness's Castle of Dark Illusions having 250'''9''' DEF.
* In the fifteenth episode of the second series anime, Yugi uses a monster called Catapult Turtle to launch a Fusion Monster, Gaia the Dragon Champion, at another monster, the Player Killer's Castle of Dark Illusions. This destroys the Dragon Champion on impact, causing Yugi to lose most of his Life Points (going from 1606 to 300 for no apparent reason) and the castle's flotation-ring to fall off, but it seemingly doesn't destroy the castle...until Yugi mentions that the Castle is now being held up by Yugi's Swords of Revealing Light (which were keeping all of the Player Killer's monsters paralyzed). Yugi ends his turn, ending the effect of [=SoRL=], thus causing the destruction of the Castle...and all of the Player Killer's monsters, which were underneath and, due to the Player Killer's Chaos Shield, couldn't get out of the way in time. If these had been real, physical creatures engaged in a battle, this would be reasonably creative and entirely valid. But they're just cards in a card game, [[MagicAIsMagicA subject to the rules thereof,]] so Yugi's trick had ''absolutely no basis in the rules'' [[RuleOfCool (but it looked cool).]]
* In the same episode as the above, the flying castle itself has the effect of hiding the villain's monsters in darkness, so Yugi can only attack the darkness and get his monsters killed by cards he can't see. How exactly is that supposed to work ''without'' holographic technology? 'You're attacking my monster? Sorry, it has higher ATK than yours. No, I can't prove it, that would defeat the whole purpose of the shrouding darkness. Just take my word for it, will you?'
* Speaking of the Swords of Revealing Light, they had a different effect in the first episode. They held only the monsters back that were present during the card's activation. But whenever Kaiba summoned another monster, the new monster was capable of attacking, while in all subsequent appearances, the Swords of Revealing Light will hold all opposing monsters back.

** Later, Yugi attacks it once its ATK was low enough for his weaker monsters to defeat it. However, it is stated that because Blue-Eyes Ultimate Dragon is a Fusion Monster that requires three Fusion Material Monsters, it must be attacked three times to completely destroy it, so Yugi's attack killed only one head. And then, Kaiba uses Monster Reborn to revive the destroyed head, returning it to the power level of a regular Blue-Eyes White Dragon. No other Fusion Monsters ever display this characteristic and this is never brought up again.

* Battle Ox, a monster without an effect, was resistent against FIRE monsters, just so Jonouchi would get a disadvantage against Kaiba. Additionally, Dinosaur-type monsters were weak against FIRE monsters for no reason (perhaps a reference to the Cretaceous extinction?), giving Jonouchi an advantage over Dinosaur Ryuzaki. This is later dropped.

* This trope is relatively justified when more than two duelists participate in a duel. The game had no 2v2 rules for some time, and there are still no written rules for anything other than 1v1 and 2v2. The solution is basically just to come up with a set of rules everyone agrees to which happens a few times in the series to allow for things like 4-player free for all.

* The Battle City rules themselves count as this. The rules used in the show were deliberately moved closer to that of the real life TCG with no greater justification than "Kaiba changed the rules for his tournament". If the new rules had just been for Battle City, it would be one thing, since tournaments sometimes use HouseRules, but Kaiba somehow makes the rule change ''permanent'': even after the tournament is over, nobody ever goes back to the pre-Battle City rules despite these being the official ones in-universe. Even players from alternate universes use Kaiba’s new rules for some reason!

* Obelisk's Soul Max effect changed during the Battle City tournament. First, it could destroy all enemy monsters and inflicts 4000 damage, but later in the finale, Obelisk's ATK increases to infinity instead [[note]] Though it bears noting that for time constraints, the anime features 4000 LP rather than 8000, so there isn't that much of a difference [[/note]]. Not only that, Obelisk changes its color when powering up, something that didn't happen with the previous Soul Max effect.
* Bakura tends to do this more often than not as his entire strategy. In Battle City, Dark Necrofear works to summon a Field card called Dark Sanctuary, which seems to be activated by the system reading his mind to see what card he designated the target without anyone else knowing. How this could actually be enforced under any situation, period, is not entirely clear though it is worth noting that this is not the case in the Japanese version. And in his final appearance, he manages to be in three places simultaneously and completely flouting the rules in all three. As Zorc, he ignores the effects of four separate all-destroying attacks. As Honda-Bakura, he uses a strategy that works purely by making his graveyard go away. The cards aren't banished and don't go to his deck or hand, which is the only place they can go, but the Graveyard just...goes away. And as the game master, [[ScrewTheRulesIMakeThem he explicitly says he's making up the rules as he feels like it.]]
** A somewhat odd example from the Dark Sanctuary duel: Yugi notes that Bakura's strategy will fail because he needs to play more than five Spell/Trap cards at once to achieve it. Bakura then says that Dark Sanctuary allows him to have more than five on the field at once. Yugi then counters that it doesn't matter what the card ''says'' - there is simply no mechanism in Kaiba's duel disk for Bakura to play a sixth card [[note]](in the Japanese version, he says that Dark Sanctuary lets him use his Monster Card Zones)[[/note]]. This is glossed over, as Bakura never gets to five anyway.

* During his Duel with Kajiki, Jonouchi's Alligator Sword is inside the Fairy Box, but when Umi is played, the monster almost drowns. Aside from the FridgeLogic that alligators cannot be drowned that easily, Umi has no effect that would harm monster cards that cannot breathe underwater, a mechanic that only works with the hologram system, or negate effects of other cards, such as Fairy Box.
* When Kaiba introduced the new rules with the Duel Disk System, Fusion Monsters couldn't attack in the same turn when they are summoned. This rule disappeared since the fourth season.

* Before the duel between Jonouchi and Rishid, people could apparently create Fusion Monsters as long they have Polymerization. When Jonouchi drew it and he had three monsters on the field, the Spell Card was useless because he cannot fuse them for some reason. Presumably, having the fitting Fusion Monster is indeed needed, even though this was never an issue before.

* ''Anime/YuGiOhTheMoviePyramidOfLight'' is infamous for its errors, with some of them involving ignoring rules or effects:
** In the simulated duel, Kaiba summons Blue-Eyes Ultimate Dragon. The writers forgot that Osiris's Lightning Blast effect would decrease Blue-Eyes' ATK by 2000. Also, Obelisk's Soul Max effect happened during Kaiba's turn, which would be impossible.

* The duel against Dartz has quite a bit of this. First, it is said that The Seal Of Orichalcos can't be made to leave the field by any means. However, Dartz does remove it, in order to activate an enhanced version, which is later replaced by an even more enhanced version. Then when the Pharaoh summons the Legendary Knights, they destroy the Orichalcos anyway. When one of Dartz' monsters is destroyed, he pays all of his Life Points to summon Divine Serpent, a monster with infinite ATK, and an effect that makes him able to continue, even though he has no Life Points. Unsurprisingly, despite being hit by an attack with infinite power behind it, [[PlotArmor the Pharaoh still doesn't lose,]] and uses a card that also makes him unable to lose, as long as he keeps his Dark Magician Girl in play. Then the Pharaoh has two of his Legendary Knights attack Divine Serpent, and make their attacks constantly reflect each other, until their ATK raise to infinity. Then he suddenly sacrifices them in the middle of an attack, so as to summon a fused form of the Legendary Knights, which gains the infinite ATK, and then is able to destroy Divine Serpent, and win the duel.

** The effect of Magic Cylinder seems to depend on the era it is played. In the ''Duel Monsters'' era, it reflects the attack to the attacking monster, and its first appearance implies the player must control a Spellcaster. In the ''GX'' era, it reflects the attack directly to the opponent, like in the real game. The latter is played early on by Sho, while the former is used by Yugi during his duel with Judai, who somehow traveled to the past.

** And later we have Yusei, Jack, and Rua creating new cards in the middle of a duel, including two different monsters from the same blank card at different points!