Please read the following rules. They do not differ from your other battles much, but these rules will be enforced more severely. You WILL be punished if any rules are broken.
The following are settings that are to be used in all Gym Pokémon matches:
•Match Type: Level 100 Standard Play Only.
•Best of: 1 match (6 Pokémon each)
In addition, the following rules apply to all Gym matches.
•Species Clause: You may not have more than one of the same exact Pokémon on your team. This does not mean that using a team of all dragon/ground will be permitted against something like an Electric team. DON'T BE CHEAP and use doubles of each type if you can avoid it.
•Sleep Clause: No two Pokémon on either team may be put to sleep by their opponent at the same time. This does not include self-induced sleep techniques such as rest.
•Self KO Clause: If both players are on their last Pokémon, and one player performs a Self KO technique such as Self-Destruct or Explosion, and both players' Pokémon faint as a result, the player that initiated the move will be the loser of the battle. This does not include techniques or items that produce recoil.
•Evasion Clause: Any moves that increase your Pokémon’s evasion skills are banned from use. This is due to the simple reason that it brings the battles to a gamble, a luck draw, if you will.
•One Hit KO Clause: Any techniques that produce a One Hit KO on the opponent are banned from use. No horn drill, sheer cold, or fissure.
•Item Clause/Restriction is ON: That means you may not use more than one of the same item.
Keep in Mind: The use of any hacked Pokémon is strictly forbidden. This means Pokémon created by Pokesav or any other cheating devices even with legit stats are not allowed. If you are caught with any hacked Pokémon, your team is subjected to being banned for a certain period of time. If you refuse, an inspection of your team by an admin or moderator to check for hacked Pokémon will ensue. Or, if you are caught lying to an admin or moderator, a strict punishment will be enforced upon you.
Make sure your Pokémon are legitimately obtained before using them. If you got your Pokémon in the GTS, check them using IV calculators. Or, if you don’t completely trust yourself, ask an admin or moderator to engage in a trade – not for Pokémon, but to check the stats of your Pokémon to see if they are legitimate. Having no “legit” Pokémon available is no excuse, even highly competitive legitimate Pokémon are not that hard to obtain.
If you want to play with Pokémon teams that have all maxed out stats, there are online simulators that allow this advantage. If you wish to use them.
My own rules:
You cannot use Supereffective moves 3 times in a row
I will think of more when i can
Source:I got the rules from my rules on Chimchar