The Pokémon Company and Nintendo haven’t been too vocal about those who got Pokémon Sun & Moon early or by ill-gotten means, but apparently punishments are being meted out. Some players are reporting that their 3DS consoles have been locked out of online services, across all games. This affects both your Nintendo Network ID (which allows you to access any digitally purchased games) as well as your individual console.
This specifically seems to happen if players try to access any online functions in the games. Guess this is your head’s up. The bans occur in waves and there is no telling if players are in for another round before the games’ release.