[Shogun]

i played a game once, that had a anti pirating protection work like this, and i thought that was pure genius!
it was a round based multiplayergame, and if a player was detected with a pirated copy of the game, the whole game would turn against him without notice.
all ia enemies would go for him first and use overpowered weapons to strip the pirate of any fun he could have in the game.

also when someone tried to cheat and was detected by the server, every other player was informed about that, but not the cheater. the game featured alliances, and everybody would ally against a cheater.
it worked very good and was a better approach than just banning, because the legit players would have the fun on the cheater instead of the other way round.

so turning the game against griefers would be the most effective way to get rid of them!