Trump told reporters late last night he’ll be withdrawing from the original NAFTA to pressure Congress to accept the new agreement, giving them a choice of the new agreement or nothing. It’s unclear he can withdraw without congressional approval; some experts say yes, some no. 
Also, we’ll see if he does it. He’s been talked out of initiating the withdrawal process before. But this is very much not what Canada, Mexico and the U.S. business community want to hear.
Judges, potentially. An attempted Trump withdrawal would be guaranteed to end up in court.
