So here's a fun constitutional puzzle: who gets to decide how much to tax imports? If you said "the President," you'd be wrong, according to the Supreme Court. And if you said "Congress," you'd be right, according to both the Supreme Court and, surprisingly, a bunch of Republican lawmakers who are now telling their party's standard-bearer to cool it.

The drama started when the Supreme Court, in a 6-3 decision, blocked an attempt by former President Donald Trump to use emergency powers to justify sweeping import taxes. The court said, essentially, "Nice try, but no." The International Emergency Economic Powers Act isn't a blank check for tariffs; that power belongs to lawmakers. It's a basic separation-of-powers thing: Congress lays taxes, the executive executes. This ruling drew a pretty bright line.

Undeterred, Trump went ahead and imposed a new 10% global tariff anyway. Then, on Saturday, he signaled he might crank it up to 15%. He's apparently looking at a different section of the law—the 1974 Trade Act—which allows for temporary tariffs to address big trade deficits. He criticized the court's decision and vowed to keep fighting for his trade agenda through other legal channels. It's the policy equivalent of "fine, I'll use the back door."

But here's where it gets interesting: members of his own party are lining up to lock that back door. Republican lawmakers are saying, politely but firmly, that this tariff order is going to face a serious challenge in Congress.

Rep. Don Bacon (R-Neb.) put it bluntly in a CNN interview: the levies "will be defeated." He predicted a majority in Congress would vote against the 10% global tariff, though he acknowledged it might not be a veto-proof majority. "I think the president is making a mistake here," Bacon said, adding the obvious but now judicially confirmed point that "tariff authority belongs to lawmakers."

He's not alone. Senate Republican leader Mitch McConnell (R-Ky.) said the Supreme Court's ruling leaves "no room for doubt" about where trade policy authority resides. Sen. Rand Paul (R-Ky.) went even further, calling the decision a "defense of our republic." That's not the kind of language you usually hear from allies about a policy from their party's leader.

On the other side of the aisle, Democrats are, predictably, also critical but are framing the ruling as a vindication of their long-held position. Senate Minority Leader Chuck Schumer (D-N.Y.) took to social media to call the tariff move misguided, accusing Trump of making arbitrary policy decisions that would leave Americans holding the bag. Rep. Adam Schiff (D-Calif.) said the ruling backs his view that Trump's tariff policy has been illegal and unconstitutional all along, calling it reckless and lacking proper authority.

So what we have is a rare moment of cross-branch, and somewhat cross-party, alignment on a fundamental principle: Congress writes the tax laws. The Supreme Court said it. Republican leaders are affirming it. And a former president is testing the limits of what he can do without them. It sets up a classic Washington showdown—not between Democrats and Republicans, but between a president's policy ambitions and the very structure of the government he once led.