I am not a lawyer, but removing the criminal classification of an activity by decriminalizing it, does not make it legal. Purely at the state level, pot was or is decriminalized by some states. It was criminal (misdemeanor?), but then decriminalized to an illegal violation subject to ticketing and confiscation of the illegal substance, but no possibility of jailtime. It is now illegal in a similar way as jaywalking, or parking at an expired meter during a time it is active, in my opinion. Decriminalize as a reduction of the classification probably just means changing a felony into a gross misdemeanor, or similar.