The Senate and the House approved the North American Free Trade Agreement in 1993. If a nation decides to withdraw from NAFTA, the agreement specifies a six-month notification process. A president, with the support of Congress, can initiate this process. And a president, with the support of Congress, can attempt to renegotiate NAFTA. What a president and Congress can’t do is willy-nilly abrogate provisions they decide are not to their liking. But that’s exactly what Congress has been trying to do for 15 years by obstructing a cross-border trucking provision.