A Clause is a restriction placed on the options battlers have other than a simple Pokémon ban. They may prevent certain teams from entering the battle or outlaw choices in battle depending on the situation. Clauses may also be used to allow things which would not be possible in a normal game without cheating, such as the use of unreleased Dream World Abilities.
 Common Clauses
 Species Clause
Neither player may enter the battle with more than one of the same species of Pokémon defined by Pokédex number. This prevents teams from using several of the same Pokémon to wear down and defeat counters. It also avoids problems with not knowing whether a Pokémon recently sent out is one that has been seen before or different, and may have a different set. Almost all rulesets enforce the Species Clause.
 Sleep Clause
A player may not put two of their opponent's Pokémon to sleep. This does not include the opponent using a move to put their own Pokémon to sleep like Rest. Some versions allow a player to put two foe Pokémon to sleep without breaking the clause so long as they could not make any other move (unable to switch or select another attack). May be enforced by a forced forfeit or an alteration to standard game mechanics which causes moves which would break the clause to always fail (though certain games such as PBR include this option). This prevents sleep inducing moves from becoming a centralizing strategy. Almost all rulesets other than VGC enforce the Sleep Clause.
 Self-KO Clause
If a player uses a move which causes all remaining Pokémon to faint, they lose. Generally used only in tournaments with time constraints which make rematches impractical to prevent ties, and 1v1 tiers where it is easy to force a tie with moves like Destiny Bond or Final Gambit.
 Item Clause
A player may only attach one of each item to Pokémon on their team. Only seen competitively in VGC.
 Evasion Clause
A player may not use a move which has the sole effect of raising Evasion, namely Double Team and Minimize. Originally created because Evasion was horribly broken in the first generation and continued through the second and third generations due to perceived, but untested, brokenness and opposition to luck. In more recent generations, it is generally used because players felt that strategies reliant on luck are undesirable rather than due to the banned moves being broken. In Generation 5, testing was conducted and a common consensus was reached that evasion moves were broken when used correctly, especially with Baton Pass. It currently applies in competitive battling in all generations.
One common criticism of the Evasion Clause is the fact that starting with the 3rd generation (or technically the 2nd), there was a proliferation of ways to handle Evasion boosts. Foresight, Odor Sleuth, and Miracle Eye all reset the target's Evasion boosts. Swift, Faint Attack, Vital Throw, Shock Wave, Magical Leaf, Shadow Punch, Aerial Ace, Magnet Bomb, Aura Sphere, and Clear Smog are all unable to miss. Thunder, Hurricane, and Blizzard become unable to miss under certain conditions (rain for Thunder and Hurricane, hail for Blizzard). The moves Chip Away and Sacred Sword and the Ability Unaware all ignore the opponent's stat changes, including Evasion. Stomp and Steamroller ignore Evasion boosts granted through Minimize, and also have doubled power against a Pokémon that has used Minimize. Finally, Evasion boosts can be erased through Haze, Clear Smog, or any form of psuedohazing, just like any other stat changes. However, all of these methods have problems that prevent them from seeing frequent use in competitive battles. Foresight, Odor Sleuth, and Miracle Eye are all completely useless except for when they can reset Evasion boosts or override a type immunity; thus, the moveslot they take up is almost always better off being filled with something else. All always-hit attacks except for Vital Throw and Aura Sphere have a base power of 60, which is not good enough to be useful for attacking purposes in competitive battles. Vital Throw's base power of 70 is barely better, and its -1 Speed priority further discourages its use. Aura Sphere is a very good attack, being a more reliable alternative to Focus Blast, but the list of Pokémon capable of learning Aura Sphere is extremely small. Thunder, Hurricane, and Blizzard only have the always-hit property in the proper weather conditions; under normal weather, they are all somewhat unreliable (assuming a lack of Accuracy/Evasion modification), and the former two become even more unreliable in sunny weather or sandstorms (both of which are extremely common in OU.) Chip Away and Sacred Sword are generally not used because the Pokémon that can learn them have alternatives which are almost always superior; Unaware is more common, but suffers from pitiful distribution (Quagsire is the only half-decent Pokémon with access to it.) Stomp and Steamroller have a base power of 65 under normal conditions, and are affected normally by Double Team, which has much greater distribution than Minimize. Finally, Haze and Clear Smog have poor distribution, and most psuedo-hazing moves become unreliable against an Evasion-boosting opponent. All of this means that the so-called counters to Evasion boosting have very little usage outside of countering Evasion boosting, and so the metagame is better served by outright banning the use of Double Team and Minimize.
 OHKO Clause
The moves Guillotine, Horn Drill, Fissure, and Sheer Cold can not be used. OHKO Clause was standard in Generation 1-4, as it was seen as turning the game into a luck-based one. In Gen 5, a number of players tested OHKO moves, and came to the conclusion that they were broken in spite of their poor accuracy. It is currently enforced in all official Smogon tiers and a majority of Pokémon Online tiers.
 Other Clauses
 Monocolour Clause
The player may only bring the Pokémon of the same color determined by the Pokédex. A list of Pokémon of each color can be found here.
 1v1 Clause
A player may only have one Pokémon in their team. Only enforced in 1v1 metagames.
 Monotype Clause
The player must bring 6 Pokémon with the same type. Dual typing is allowed, but they must all share a common type.
 Freeze Clause
Two or more Pokémon of the opponent's or your team cannot be frozen at the same time. Freeze Clause was removed from standard play, as it does not adhere to mechanics and provides minimal, if any, improvements to any metagame.
 Simulator Clauses
The Pokémon Online simulator has Sleep, Freeze, Item, Species, and Self-KO clauses built in as checkboxes on the challenge window. Metagame specific clauses such as mono color are enforced by server scripts. There are additional clauses available to players as well.
 Challenge Cup
Enables Challenge Cup mode and Level Balance, in which both players' teams are randomized (with some restrictions to prevent Pokémon having no offensive moves).
 Disallow Spects
Prevents spectators (other than those with moderator or higher authority) from watching a match.
 No Timeout
If this is enabled, then that means players will have an infinite amount of time to finish the match. This is not recommended, as it will allow people to stall you out if they are losing. With timeout on, they will lose after 5 minutes of inactivity. Performing an action in the battle adds time to the clock.
 Wifi Battle
This will make the battle Wi-fi and enable Team Preview. Enabled in all Wi-fi tiers.
- Removing/Fixing outdated clauses, Smogon's Policy Review