Officially Pokemon from generators like PokeSav aren't allowed.
Eat those words! Say that to the person at rank 508 of VGCS Winters Master Division.
...Do you not understand what "officially" means?
The use of external devices to modify or create items or Pokémon in a player’s party is expressly forbidden. Players found to have Pokémon or items that have been tampered with will be disqualified from competition, regardless of whether the Pokémon or items belong to that player or were traded for.
So, OFFICIALLY, it's not allowed. Can you sneak your generated pokemon into the tournament? Absolutely. But that doesn't change the fact that it's not allowed.