oh :s sorry, I thought you knew about standard clauses.
There are some clauses for standard battles, one of them is sleep clause. You can't put more than one pokémon to sleep (self induced sleep, like resting pokémon doesn't count).
There are some other clauses, like species clauses (can't have twice the same pokémon). They are all listed in this thread I found.
http://www.serebiiforums.com/showthread.php?t=207754