If you're playing with your friend, you just have to agree that if one of you breaks the rule, that person loses. There's no in-game enforcement on the 3ds. On Pokemon Showdown as Nova says a second sleep move will just fail and say "sleep clause mod activated."Is the Sleep Clause ever enforced? If so, when and how? (My friend thinks it's a stupid rule and thus ignores it all the time, and I've never seen anything on Showdown that stops people from spamming Dark Void or Lovely Kiss or Spore, for example.)