@vault-boy There is a check run against every pokemon submitted to compete in the event. I'm not aware of anyone being disqualified from the event here in Kona, but I do know that there were a couple conversations with players about "legal" but questionable tactics, and some changes made to rosters.
In addition, there are some tournament rules that restrict this. There are no duplicates allowed in a party, so Mewtwo number 2 and above would just stay chillin at home, and probably complain that they didn't get to come to Hawaii. That first Mewtwo would be grateful to you for taking it along, but you probably wouldn't feel the same way; haven't seem to many players with top records bringing Mewtwo to battle this weekend.
ahalavais' comments