Flexible Tourney Rules

Tendency of a Tournament Arc that goes on a long time to feature an increasing amount of bizarre characters with abilities which could technically violate predetermined rules of the event. This will be ignored or actively encouraged. The hero, in contrast, will not resort to these tactics; if he does he is inexplicably reprimanded.

Makes slightly more sense if the tournament is organized by villains who will change the rules on a lark for entertainment value.

See also Unnecessary Roughness. Spontaneous Weapon Creation, when it's an extension of a person's ability, is one of the more common forms of abusing this trope.

Anime And Manga

 * In Yu Yu Hakusho, the Dark Tournament is run by a bunch of rich men who have a mutual interest in killing Yusuke (the main character) and his teammates. Thus the rules change in order to inconvenience and/or cripple Team Urameshi... until the one member of the rules committee not interested in Yusuke's death has the other members killed.
 * Even in the normal tournament battles, the team captains are allowed to agree upon a set-up that they'd think would be most interesting. The default is one-on-one with the combatants being whoever felt like going (although team captains go later in a round to conserve their strength), first team to get three victories advances (although they can go to five victories). There are also battle royales (including a five-on-one, at the solo fighter's request). Other variations shown in the Dark Tournament involves rolling dice to determine the match-ups and, when two fighters were exhausted, they were allowed to do a sudden-death match where whomever was pushed past a line lost. The referees are also allowed to delay the ten-count to give a fighter more time to get up or get back in the ring. The final round, however, is implied to be a mandatory one-on-one with each fighter only being allowed to fight once.
 * The GX Tournament in the second season of Yu-Gi-Oh! GX attracted numerous shady characters, from the megalomanical to brainwashed minions; this was allowed, because the whole thing was just a trap to fish out the person who stole yet another super-powerful card strong enough to destroy the world.
 * Averted in Mahou Sensei Negima (the original manga) where the Tournament in fact allowed almost every form of combat (non-bladed weapons, no-incantation magic, Ki Attacks, and other oddball techniques) - on the one occasion where a rule was broken, the guilty  immediately lost the match.
 * Both Evangeline and Setsuna later broke the no-incantation rule. Sort of, as the referees weren't able to note and call them on it. Eva immediately canceled her spell and apologized (of course, she soon started using the same spell sans incantation), while Setsuna's spell/prayer is forgivable as she thought she was about to die.
 * The Kujibiki in Kujibiki Unbalance is ostensibly a contest in which teams of four high school students compete to become the next student council. As we see more competitions, however (particularly in the Recap Episode), it becomes increasingly difficult to believe that all the competitors are actually students at the same school. And one time, the heroes have to face seven opponents at once, which is handwaved as a "numerical coincidence".
 * Angelic Layer. Electric whips are banned. So are projectiles. Apparently nothing else is. This includes hacking the program, exploiting a programming error in earlier models, and modding the dolls to give them extra abilities (we've seen wings and a forcefield).
 * Said electric whip is illegal because it harms other players instead of their dolls, not just by some arbitrary rules. Also modding the doll is a part of the game.
 * Just about every duelist ever in Yu-Gi-Oh!. Several of them claimed to have psychic powers, which should probably count as an unfair advantage even for the ones who weren't cheating and feigning magic to cover it. One duelist tried to kill the main character with flamethrowers over a children's card game. And the main character has a ghost in his head that plays for him who can apparently rearrange his deck to draw whatever he wants, and who can destroy people's minds with his magical powers, although he usually has the decency to win the duel first.
 * This is, of course, mercilessly mocked in the Abridged Series. "Stop this duel immediately! It violates Battle City rules! ...just like 99% of the other duels that I refused to stop."
 * In G Gundam, the rules of the Gundam Fight let the participants get away with murder - literally, in some cases. In fact, Rule 7 specifically says "Destruction of property on Earth due to the Gundam Fight is not considered a crime." Thus you get situations such as one fighter assassinating his opponents before their matches, rampant and obvious cheating, and the use of The Virus to enhance one's abilities to the point where they're effectively immortal. The only rule specifically established to prevent death says that fighters are banned from targeting their opponents' cockpits - and Laughably Evil President Evil Wong Yun Fat eliminates that rule in the Finals, using his privilege as the host nation's leader.
 * In Saint Seiya, by divine decree, of all of Athena's Saints only the Gold Saint of Libra is allowed to wield weapons (and indeed, nearly every part of the Libra Cloth is a weapon. Even its shields.) Doesn't justify the iconic Nebula Chain wielded by the Andromeda Saint, the Chameleon Saint's whip, the Auriga Saint's discs or the Cerberus Saint's morningstar.
 * Davy Back Fight from One Piece? The entire thing was rigged, with the referee on the opposing team. It was outright acknowledged that outsiders were allowed to interfere with the Long Ring Race, but during the Groggy Ring event, the levels to which the Foxy Pirates went to cheat were plain ridiculous.
 * This included using weapons in a game where weapons were exclusively forbidden, leaving the ring and returning later when doing so was also a clear foul, and trying to eliminate the Strawhat team members for 'mouthing off' to the ref. In fact, they used multiple weapons, and even changed weapons during the match.
 * Kenichi: The Mightiest Disciple had the Desperate Fight of the Disciples tournament, where the referee A. was evil. and B. admitted to just letting anything go as long as it was entertaining.
 * One chapter of Sora no Otoshimono had a wrestling tournament where this trope is averted twice. First is when Ikaros gets immediately disqualified for Beam Spam-ing, and second is when is barred from winning when it's pointed out that  didn't join from the start and only went in during the Tomoki and Mikako's match.
 * Averted in Dragon Ball, where the Man Wolf pulling a knife gets him disqualified, and so does Cyber Tao Pai Pai revealing his hidden sword. Otherwise is played straight, as Ranfan breaks the "no crying" rule with her Wounded Gazelle Gambit and nothing happens to her and Krillin throwing a pair of panties to distract Dirty Old Man Jackie Chun is fine as well. But Goku using the Kinto'un to come back is only given an one-off pass and would get him disqualified if he did it again. However, they don't seem to mind him taking off Muten Roushi's sunglasses to protect himself from Tenshinhan's Sun Fist. Groin Attacks are also banned, but we see an instance where Yamcha gets nailed and his opponent isn't disqualified because it was an accident (Yamcha did a jump kick, the other guy ducked, and his head happened to impact Yamcha's crotch), like the way Shen (said opponent) defeated Yajirobe earlier on. Speaking of Shen, there's also the little bottle he pulls out to use the Mafuuba, but it's Justified cause the announcer says "It doesn't look like a weapon, more like some kind of spell, let's see what happens."
 * In Beyblade G Revolution, normally a match consists of three 1-vs-1 games. However, a match can instead consist of a single 2-vs-2 game, but only if both teams agree.

Fan Works

 * In The Tainted Grimoire, during the Camoa Cup, Acidwire requested a single duel to decide the match between them and Clan Gully rather than the best of three that was supposed to happen. They got away with this because when they requested this, they made it seem like they were doing it out of consideration of the fact that Clan Gully has yet to recover properly from their last few matches when actually it was so they could make it easier for them to defeat Clan Gully..

Film

 * The live action Speed Racer movie, one of the drivers pulls a gun on Speed and spectators react with shock and alarm, making it quite clear that he'll be disqualified. Makes sense ... except that virtually every car in the movie is literally an arsenal on wheels and the drivers spend the race trying to kill each other with explosives, wheel-mounted drills, giant spiked balls that drag behind a car on chains, and even a beehive launching catapult in full view of the commentators and audience without anyone batting an eye. Apparently only really goofy weapons are permitted.
 * It's explicitly stated that those were illegal modifications, and vaguely Handwaved by the fact that they were all driving under a giant dust cloud that apparantly only shows up on camera.
 * Mortal Kombat: Let's just say Shang Tsung's tournament structure is a bit....suspect.
 * In the finale of Ip Man 2, wherein our eponymous Chinese Warrior and folk hero starts to win against Twister, the bloodthirsty Chinese-bullying British boxer, the referees "suddenly" remember that you're not suppose to kick in western boxing matches and call Ip Man on it; something they didn't bother to call on in the last match when Twister was having an orgasm beating a sick-and-elderly Chinese Warrior to death.
 * In Tekken Kazuya takes control and suddenly declares the tournament fights to be death matches partway through the tournament. One wonders what the other corporations that provided fighters for it thought of this.

Literature
"Ender: "It doesn't matter if you try to beat me unfairly. I'll beat you unfairly first.""
 * In Ender's Game, the Battle School setting revolves around students playing a zero-gravity war simulation against teams of their peers. When the teachers realize that Ender might be the natural General they've been waiting for, they start stacking the odds against him to see how he responds to pressure (making him fight two battles in one day, pitting his team against two teams at a time, etc.). Eventually, when he gets into the simulations against the buggers, he realizes that he had it easy at that point.
 * Eventually Ender gets fed up with the constant screwing of the rules and sarcastically suggests a match with his team in a cage without guns.
 * A secondary lesson taught was to ignore the perceived "rules" of combat. Most of the Battle School commanders, smart though they were, could not break out of certain lines of thinking (such as the practice of moving in formations during battle). Ender starts thinking outside the box and royally owns everyone he goes up against, culminating in winning an impossible fight by performing the victory ceremony before the battle was over.


 * They specifically mention that it would take at least a year for the Battle School to recover from Graff's changes meant to train a single student. Of course, the Battle School is disbanded even before the end of the Bugger War.

Video Games

 * Despite being a game about boxing, Hoy Quarlo in Super Punch-Out!! uses a cane, Dragon Chan mixes flying kicks in with his punches, King Hippo straps a manhole cover to protect his stomach and so on, and so on.
 * Common in The King of Fighters - Whip brings a gun to a martial arts tournament, in addition to her namesake weapon. Then again, there has yet to be a single King of Fighters tournament that wasn't used as a front by that year's villain, to the point the Heidern Mercenaries go on red alert every time they get an invitation.
 * Considering almost every character in the series can use some form of Ki Attacks, this is probably allowed because neither Whip nor Yamazaki, who has a handgun and a switchblade, have attacks like that and thus they are at a disadvantage without them.
 * Yoshimitsu and Kunimitsu from the Tekken games seem to not object to bringing knives and swords to the fistfights.
 * With all the Cyborgs and Robots around, this hardly seems a big deal. Not to mention pandas and bears (oh my).
 * Street Fighter's Vega (or Balrog in the original) uses a claw in his fights. The White Wolf RPG tried to explain this as saying he fought in a weapons-using division, but it didn't explain why he was allowed to use it against fighters who weren't pro-weapon.
 * There's a simple reason. The tournament is being run by Shadoloo. Vega works for Shadoloo. Justified Trope.
 * Give the guy a break. He's one of the only fighters in the game without a Fireball Attack.
 * Any tournament that allows martial artists to attack each other with fire - even if they're generating it out of their own bodies - probably has little in the way of actual "rules."
 * C.Viper's use of a weaponized suit is often Lampshaded in Street Fighter 4.
 * Not a tournament, but the double standard in the Ace Attorney trials is staggering. The judge is shown to disapprove of intimidation from the defense in the courtroom, but has no qualms about the prosecutor frequently and indiscriminately using a whip. A prosecutor presented forged evidence, he got a penalty. When the defense was accused of such, he got disbarred. Heck, Phoenix was once penalized for finishing the judge's sentence.
 * Even worse? Japanese lawyers confirm that this is Truth in Television. What.
 * The Colosso tournament in Golden Sun, where the player is allowed to get help from the other party members to cheat on the obstacle courses, and the enemies in the battle portions use only physical attacks while you have Djinn and Psynergy.
 * Justified by the fact that the Ruler of Tolbi and host of the tournament told him to do that in order to see his powers.

Web Comics

 * In the web comic Yet Another Fantasy Gamer Comic, one of the recent story arcs had players competing in a tournament with increasing convoluted cheats by the hobgoblins, which in the end have to be accepted due to a loophole in the rules that says the contestants use the rules from their own country.
 * Done in Sluggy Freelance when they parody the Tri-Wizard tournament from Harry Potter. Any message that comes out of the "Goblet of Flameyness" forms a Magically-Binding Contract, so anyone who tampers with the goblet can create whatever rules or exceptions to rules they want. This includes having an olympic athlete compete in a student competition, expanding the number of competitors from three to five, and having one of the Duh-Mentors compete.
 * This trope sometimes turns up even without goblet tampering, however. Such as when Torg takes "use the tools around you" to mean he can grab someone out of the audience and have her fight a giant monster for him.

Western Animation

 * In The Legend of Korra, Avatar Korra Invokes this as a justification for being able to secretly compete in Pro-Bending in spite of being the sole person on Earth to command multiple Elemental Powers where other players' only have one. To compensate, she promises her teammates that she'll confine herself to waterbending. When she reflexively simultaneously bends three elements out of frustration after committing two consecutive fouls, she's publically outed, and the referee stutters "Foul! ... I think." The only reason this display is not counted against her is that the referee hasn't foreseen the circumstance. After some deliberation, the referee Averts this by codifying the Obvious Rule Patch, allowing her to play on the condition that she only Waterbends.

Real Life

 * In a tournament held in the 13th century, a famous noble arrived with his warriors and announced that he would only be watching, not fighting today. Much later in the day, after having time to study the other fighters and let the other fighters grow tired; the noble announced that he had changed his mind.