Selective Enforcement

One character sees another getting away with something that is against the rules. If he speaks up everyone ignores him. So he decides to join in, and commits some very minor violation. He is immediately caught and has the book thrown at him.

Almost always played as comedy trope, this trope can range from a single scene to a whole plotline. It is is rarely done as drama, despite the dramatic potential. It is a fairly subversive trope, showing a poor fit between actions and consequence.

See also Arson, Murder, and Jaywalking. Can be related to Can't Get Away with Nuthin'. If someone tries to imitate the Karma Houdini, they'll end up like this. Protagonist-Centered Morality would be a subtrope of this.

Examples of Selective Enforcement include:

Film

Anger Management centers on this trope. An excessively passive man is sentenced to anger management classes for allegedly (but not really) starting a commotion on an airplane. And it happens again, each time with him accidentally insulting or harming a woman/ disabled person/ ethnic minority that would ensure that no jury would pity him. It was all a Massive Multiplayer Scam, with these manipulative folk being presented as the good guys.
- Except the guy with the tazer. He was just having a bad day.
Outlaw playes the trope straight for drama. In the film, the London Metropolitan Police is horrendously ineffective at dealing with professional criminals and hooligans, but when the protagonists form a vigilance committee and start beating up dealers and robbing money launderers a corrupt cop turns them into public enemy #1. 2/3rds of the remaining protagonists wind up getting gunned down by armed Flying Squad members in the end.
Bicycle Thieves: A non-comedic example is this classic Italian film. The protagonist, Antonio, has his bicycle stolen which he needs for his job. Eventually, he tracks down the thief, but the police lets him go, because Antonio doesn't have any proof and his neighbors lie for him. Out of desperation, Antonio tries to steal a bicycle himself, and is caught immediately.

Literature

In the Wayside School books, Todd always gets in trouble three times over the course of the day and is always sent home early on the kindergarten bus. On multiple occasions, this is due to a selective enforcement plot when the rest of the class gets away with things, but he gets caught for a minor infraction. For example, the whole classroom will be talking loudly with the teacher not paying attention, but the second Todd opens his mouth, the entire class is silent and he's caught talking in class.

Similarly, one scene has Joy bugging him over what page he's on in the math book, and mocking him for being so far behind her. Her mocking gets very, very loud. But when he finally loses his cool, he's the one who gets in trouble. Immediately after he saved the lives of everyone in the class.

Live Action TV

In Becker, Dr. Becker makes several attempts to go see a particular movie which fail because of loud, disruptive people in the cinema. At a later attempt he practically gets crucified because Margaret keeps talking to him.
In Friends, Ross finds out that students are sneaking library stacks for sex (particularly the aisle containing his thesis). The library refuses to do anything about it. He decides to monitor the aisle himself, meets a pretty grad student... and ends up getting caught by the librarian.
How I Met Your Mother: Marshall talked his way out of a ticket by offering to bring the cop to his barbecue. Robin, being a pretty girl, can get out of a ticket easily. Barney? No way.
Used in Police Squad!! when Frank Drebin is trying to goad "The Champ" into accepting a prize fight with Bobby Briggs.

Frank Drebin: Bobby Briggs could break every bone in your body.
The Champ: Yeah, well he must be a pretty good boxer.
Drebin: Well, how would you know? You never won an honest fight in your life.
The Champ: Hey, take it easy. Nobody wants to get hurt. Just cool off.
Drebin: Why should I? The only reason you're champ is cause of guys lying down or dying.
The Champ: Hey, let me buy you a drink.
Drebin: I wouldn't drink with you, you two-bit phony excuse for a fighter.
The Champ: You're just tired. [pats Drebin on the cheek] You didn't mean it.
Bobby Briggs: [to Drebin] Aw, forget it.
The Champ Forget it? Nobody says "forget it" to me! [takes a swing at Briggs]

Happens a lot on The Andy Griffith Show whenever the plot requires it. Andy seems less intent on actually enforcing the law than he is in promoting his own sense of values, and it always seems to work out. Barney, on the other hand, can't seem to tell where to draw the line on anything he's involved in.

Video Games

In The Elder Scrolls, most of Tamriel is above the law. In Morrowind or Oblivion, if they slept on the street, the guards would simply get stuck trying to walk over them. You decide to do the same and are right there yelling "STOP RIGHT THERE CRIMINAL SCUM!"

Webcomics

In Subnormality, there is a page featuring a man trying to sleep who cops this trope.
This happens in Ozy and Millie, due to the author's bad experiences in school.

Western Animation

In the South Park episode, "Fingerbang", the mall security guard allows a mad scientist with a jar full of anthrax to pass by, but will immediately attack anyone else with pepper spray for even a minor rule breach, if even that.
- Butters is this trope personified.
The Simpsons
- In one episode of Lenny and Barney play pranks on Moe which involve setting him on fire and setting a cobra on him. Homer, in an attempt to join in the "harmless" fun loosens the lid on a sugar cellar, resulting in what Moe angrily calls "the old sugar-me-do". This gets Homer banned from the bar.
- A darker comedic version is played out with Homer and Frank Grimes. When Frank Grimes tries to live and work like Homer does, but quickly discovers that only Homer can grab high-voltage wires without safety gloves and live.
- In "The Monkey Suit," Chief Wiggum arrests Lisa for teaching her classmates about evolution (which got outlawed and she was rebelling against that rule). She protests that there are much worse crimes, pointing to Snake, who is shooting people from atop the Kwik-E-Mart. Wiggum explains that it's because they only have enough funding to enforce the most recently created law (thus literally "selective enforcement") although Wiggum does admit is "not the best system - in fact it's pretty much the worst."
Invader Zim: In the episode "Parent Teacher Night", everybody is conveniantly staring silently in the opposite direction of the mess loudly made by Zim's robotic parents. But after they leave, and Dib tosses his juice cup to the ground in frustration, someone turns around and shouts "Hey! That kid's throwing punch!" and the episode ends with Ms. Bitters descending on Dib like the wrath of ~~God~~ some kind of snaky demonic Satan thing.
Foster's Home for Imaginary Friends: Inverted as a Springtime for Hitler in the episode "Crime After Crime". The episode's B-plot has Frankie cooking something disgusting for dinner, so Bloo causes trouble in an effort to get sent to his room without dinner. Unfortunately the episode's A-plot was Mr. Harriman acting hyper-paranoid over someone discovering his addiction to carrots, leading him to punish everyone else in the house for relatively minor infractions due to thinking they're "on to him" while completely ignoring or even congratulating Bloo.
SpongeBob SquarePants: In Bikini Bottom, harassing your business rival to near-suicide, destroying stuff because you've got the IQ of a turnip, or being an all-around annoying jackass with No Indoor Voice is perfectly acceptable. Littering, however, can get you an orange jumpsuit. Just ask Squidward or Mrs. Puff.
In the episode "The Runaway" of Avatar: The Last Airbender, Toph spends much of the episode pulling pranks to Fire Nation's swindlers for money and for fun, Katara becomes mad at her because Toph might get them into trouble, Toph snaps back by saying that Katara is no fun, then to prove that this is not true, Katara plans a big prank which requires Toph's help; As expected they get caught because they fell into an enemy's trap.
King of the Hill: After Bill is jailed for public intoxication, he refuses to see anyone - so Hank tries to get himself arrested and get thrown in with him. The cops don't care about him jaywalking on an empty street, and wearing "No shirt, no shoes" in a convenience store only breached store policy. However, a low-speed collision that scratches an officer's kid's "honor roll" bumper sticker gets him cuffed and thrown to the wall.