U.S. trade partners and business leaders are hoping the Trump administration will refrain from the auto tariffs that have long been under consideration, but the recent U.S.-Mexico-Canada Agreement on trade may give the administration an extra incentive to add them.

That’s because one of the main features of the USMCA is a change to the “rules of origin” for autos: how much of the car must be made in north America for it to be duty-free. In order for those rules to have real teeth, according to trade experts, they may need to be accompanied by the tariffs.