But over the last 50 years, Congress has delegated the bulk of its trade power to the president, and there isn’t much expectation that it’ll wrest it back anytime soon. “To claw those powers back would in effect take veto-proof majorities coming out of the House and Senate, and I just don’t see that as remotely likely in the current circumstances,” said Edward Alden, a senior fellow specializing in trade at the Council on Foreign Relations. “So I think the president does hold all the cards here.” Trump is imposing the tariffs under a provision of the Trade Expansion Act of 1962 that allows the president to do so for reasons of national security. That rationale has rarely been used, trade experts said, and it could lead other countries to cite their own national security to restrict imports of U.S.-made products.

A Republican congressional aide, speaking on the condition of anonymity to discuss a sensitive policy topic, said GOP leaders “won’t rule out potential action down the line.” But the vagueness of that threat itself underscores the reluctance of Ryan and Senate Majority Leader Mitch McConnell—who has said nothing publicly on tariffs—to take Trump on so directly. To have any chance at success, they’d have to muster an overwhelming majority of Republicans, because Democrats remain deeply divided on trade. Even then they might fall short. When former President Barack Obama sought authority to negotiate trade agreements that would not be subject to amendment by Congress, all but 28 Democrats voted no. The trade deal he ultimately struck, the Trans-Pacific Partnership, never even received a vote.