"The administration does not have the unilateral authority to pull out," Toomey told CNBC News. "NAFTA wasn’t actually a treaty, it’s an agreement. But it was made operative by legislation in 1993 Congress passed a law, the president signed it, that’s what put NAFTA into effect. The President doesn’t have any more authority to repeal that law that he has the authority to repeal Obamacare or change taxes."
READ MORE: New Round of NAFTA Talks in Washington Hitting 'More Intense Period' — Freeland
In an opinion article, Toomey wrote for The Wall Street Journal on Friday, the senator said the Trump administration will have a fight on its hands if it tries to leave NAFTA without the consent of the US Congress.
Trump has threatened to leave NAFTA if a better agreement is not negotiated between the United States, Mexico, and Canada, claiming that NAFTA is unprofitable for the US. The current agreement has been in place since 1994.