The Obama directive was not law. It wasn't even an Executive Order.
All it consisted of is a letter (2 letters actually) advising the States that he would punish them if they didn't jump through his Fascist hoops. It would be like me writing you a letter stating, "If you don't paint your house green I'll be mad at you and there will be consequences". Of course a presidential letter carries quite a bit more weight than a letter from me.
Trump merely made it known that there's a new sheriff in town and this is a State by State issue, not a federal issue.