So, I'm not familiar with the Tournament scene, but what is to prevent someone coming in with a Spiritomb with Wonder Guard? Or have a Pokémon with an attack that it does not get via level up, TM/HM, or breeding? Or base IVs that are all maxed thanks to an Action Replay? Sure, the last could be done with hours of breeding and/or luck, but the possibility is still there for this.
Are there any safeguards in place that prevent overly hacked Pokémon?