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.
In the case of an attack that causes recoil damage leading to both players losing their last Pokemon, the one who took the recoil damage (the one whose attack was the final event of the match) will be given the win. Various Official Nintendo tournaments handle this differently, but all Wifi and Wireless battles follow the rules above.
 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 it has been deemed broken since generation 1, the Evasion Clause is one of the most consistent clauses in competitive Pokémon, having been retested on occasion (with the most recent being at the start of Gen 5), and still being found broken, not to mention uncompetitive.
 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.
 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