The two stroke ban WAS an EPA compliance move.
Or are you telling me that it’s legal to drive around with no catalytic converters if your vehicle was so equipped when new?
Not, this would be like requiring cats to be added to older legal vehicles.
you do not need a seat belt or a catalytic converter on any vehicle that was not equipped when new...and it is perfectly legal to drive such vehicles today.
That isn’t a state licensing issue unless the state chooses to make it one. I’ve yet to see Federal Marshalls stopping dirt bikes for EPA compliance on any road around here (although federal employees could enforce similar regulations, such as for spark arresters, on federal land).