No Hugging, No Kissing, No PDA of any kind!
The penalization of romance stems from the idea that The Power of Love either Makes You Evil, Crazy, Uncreative or just plain Dumb. Love just seems like a bad idea, so what better way to better the human condition than just banning love all together?
This is a strange, if-not impossible law to regulate and enforce in real life, so those that enforce it are foolishly idealistic at best, unreasonable and tyrannical at worst, inspiring various rebellions of various shapes and sizes in the process. The Evil Overlord behind it could have a variety of reasons for doing so. They could have had a personal experience with failed love, thinking that if they can't have love, then no one can, or maybe they feel that they are committing a service to others and preventing heart-break. If completely eradicated from society, people could ask "What Is This Thing You Call "Love"?"
- After Queen Freya from The Huntsman: Winter's War sees her lover Andrew murder her infant daughter when in actuality, he was being controlled by her evil sister Ravenna, she kills him with her dormant magical powers and conquers the north. She then abducts the children of that land, trains them into her own, personal army, and then makes love a crime punishable by death.
- The state of Libria in Equilibrium criminalizes love alongside all other emotions, and legally requires the population to take emotion-suppressing drugs. It is strongly implied, however, that even drugs cannot fully eradicate human capacity for love, since even John Preston, who dutifully took them all his life, displayed behavior consistent with emotional reaction when the state took his wife away from him.
- Played with in the Delirium Series. Love itself (the novel's focus is romantic love, but it's made clear that it applies to all love) is a mental illness, and objecting to the "cure" is considered criminal.
- Both physical and emotional love are forbidden in 1984 because the only acceptable attachment is devotion to Big Brother.
- In the Free-Love Future of Brave New World, not just monogamy but feeling too strongly attached to someone is highly frowned upon and considered backwards and unnatural, if not outright illegal (Lenina's friend encouraging her to be "more promiscuous" to avoid trouble could very well mean "be more promiscuous so you're not suspected of breaking the law").
- The Peacekeepers in Farscape are totalitarian Commie Nazis, and a totally military society who use The Spartan Way for upbringing. While non-procreative sex is accepted as a form of physical recreation, any form of emotional relationship beyond military comradeship is absolutely banned. When one female character was discovered to have fallen in love with a man and conceived a child by him without eugenic selection, she was forced to choose between killing her lover or child.
- If Love Was Illegal by David Olney.
- According to one Christian legend, in 3rd century Rome, an emperor by the name of Claudius issued a decree to his soldiers that they were forbidden to marry. A guy named Valentine defied this decree and issued marriages to the soldiers in secret. Claudius found out, was furious, and had Valentine beheaded. Thus, one theory on how the legend of Valentine's Day was born.
- In Once Upon a Mattress, Queen Aggravaine passes a law banning her subjects from marrying until after her son is married, in hopes that her subjects will inspired to find a suitable princess. Since the women of the kingdom aren't interested in being wooed unless there's a hope of getting married, the marriage ban effectively serves as a ban on courtly love as well.
- In The Mikado, the emperor has decreed flirting is punishable by death. As of the beginning of the opera, the authorities have been getting around this by appointing Ko-Ko, a condemned man, to the office of executioner. Since he is the next man scheduled to die, no one else can be executed for flirting until he is, and since he's not planning on executing himself, there have been no executions.
- Some very extremist totalitarian regimes took control of everything, including who can marry, how and when, and repress sexuality, cases like China during Mao's Cultural Revolution, Pol Pot's Cambodia and to a lesser extent Stalin's USSR.