>>15868879>Legality checkers>Doing shitLegality checkers only stop the most blatant of fakemon.
Additionally, once you have cracked it in any firmware, there's no way to distinguish old legitimate pokemon that pass the old checks from hacks that pass the old checks.
You have the option of either disqualifying all old pokemon like that from going online every time you update or allowing the hacks made in old firmware to come through as legal, as they are indistinguishable otherwise.
This is, for example, why DSi flashcart security was so halfhearted. The DSi could block the names of flashcarts if their header did not match legitimate games, but any legitimate game that passed the header check could run.
