I know you've been waiting for this Richard! Here's the rules:
It will be 6 vs. 6 teams in single battle mode, it is not required to have 6 pokemon on your team, although it is highly recommended
Team Preview (no one can control this, just something to add in to be safe)
Species Clause (This means no more than one pokemon of the same species can be on your team. This also means that different forms of the same pokemon, for example, rotom, can't be on the same team.)
Sleep Clause (Means that no more than one pokemon on your opponents team can be put to sleep by one of your pokemon at a time. If they use a move like rest, for example, to put one of their own pokemon to sleep, that will not activate the sleep clause.)
Evasion Clause (No evasion boosting moves, for example double team, are permitted)
Freeze Clause (No more than one pokemon on a team can be frozen. This clause shall be enacted without control)
Weather is allowed this time, since none can cause it automatically upon switch in.
Only NU (NeverUsed) pokemon are permitted.
Please note this is on Pokemon Showdown
Members entered:
ShinyBlaziken2000
Liam
JSM