At Volokh Conspiracy, Ilya Somin says they are: Why Trump's "Liberation Day" Tariffs are Illegal – They weren't authorized by Congress and go against the major questions and nondelegation doctrines. From the introduction:
The enormous scale of the new Trump tariffs is at the heart of their illegality. In an earlier post, I explained why Trump's earlier use of the International Emergency Economic Powers Act of 1977 (IEEPA) to impose 25% tariffs on Canada and Mexico is illegal and unconstitutional under the major questions and nondelegation doctrines. This much larger abuse of the IEEPA is even more clearly illegal.
As GOP Senator Rand Paul put it, in a speech denouncing the new tariffs: "One person in our country wishes to raise taxes. This is contrary to everything our country was founded upon. One person is not allowed to raise taxes. The Constitution forbids it." Exactly so. The Constitution gives Congress the power to impose tariffs, and the President cannot exercise it without, at the very least, having much clearer congressional authorization than exists here.
The IEEPA gives the president authority to impose various types of sanctions in situations where there is "any unusual and extraordinary threat, which has its source in whole or substantial part outside the United States, to the national security, foreign policy, or economy of the United States, if the President declares a national emergency with respect to such threat."
On the major questions doctrine:
In recent years, the Supreme Court has invalidated a number of executive initiatives under the "major questions" doctrine, which requires Congress to "speak clearly" when authorizing the executive to make "decisions of vast 'economic and political significance.'" If things are unclear, courts must reject the executive's assertion of power.
If Trump's sweeping use of the IEEPA to start the biggest trade war in a century does not qualify as a "major question," I don't know what does. Trump's "Liberation Day" makes even Joe Biden's $400 billion student loan forgiveness plan (which I opposed, and which the Supreme Court rightly invalidated under MQD) seem modest by comparison.
And, it is at the very least, far from clear that the IEEPA authorizes the use of tariffs, that we have an emergency here, or that there is any "unusual and extraordinary threat." If any of these three preconditions are not clearly and unequivocally met, then the major questions doctrine requires the courts to invalidate the tariffs unless and until Congress enacts new legislation clearly authorizing them.
And on delegation:
In addition to running afoul of the major questions doctrine, Trump's new IEEPA tariffs also violate constitutional limits on delegation of congressional power to the executive. Even if Congress did clearly authorize these measures, it cannot give away its authority to the president on such an enormous scale. Admittedly, the Supreme Court has long taken a very permissive approach to nondelegation, upholding broad delegations so long as they are based on an "intelligible principle." But, in recent years, beginning with the 2019 Gundy case, several conservative Supreme Court justices have expressed interest in tightening up nondelegation rules….
I think both points are probably right from an originalist perspective. As to the major questions doctrine, I agree it's hard to say either that the IEEPA is clear or that the tariffs aren't a major question. The only originalist counter, as I see it, is that the major questions doctrine is inconsistent with originalism (though I argue that it is). But one might not even need the major questions doctrine, as it seems somewhat doubtful that even a straight textualist reading of the IEEPA would permit the tariffs.
As to delegation, I have not come to a firm conclusion about the original meaning and nondelegation as a general matter. But it seems that the Constitution probably contains at least a weak nondelegation rule, based on the vesting of the legislative power in Congress. And as Professor Somin says, even a weak rule might invalidate this delegation. I would be interested to hear what opponents of a historical nondelegation doctrine, such as Julian Mortenson and Nicholas Bagley, think on this matter.
The main modern counterargument, even from those who endorse the major questions doctrine or the nondelegation doctrine in domestic matters, may be that foreign affairs are different. I think that distinction lacks originalist foundations. It's true that (in my view) the President has substantial independent powers in foreign affairs, and delegations in areas associated with those powers may be more acceptable. But even if true, that should not affect the assessment of delegations in foreign affairs areas that are not independent presidential powers (like tariffs). (My recent co-authored article on delegation of war powers touches on this issue.)
The problem, in my view, is that the courts, commentators and the political branches have indulged very broad delegations in foreign affairs in the name of expediency. It may be very hard to take that back.
UPDATE: Steven Calabresi agrees: President Trump's New Tariffs Are Unconstitutional.
He makes an additional important point: there's nothing inconsistent about having a strong view of presidential power (such as thinking, as he and I do, that the President has constitutional authority to control the executive branch) and yet a narrow view of the President's power to exercise what appears to be legislative authority (such as imposing tariffs). Indeed, that is the essence of separation of powers. Separation of powers does not mean a weak President. It means a President who is predominant within the President's field of authority but lacking in power within Congress' field of authority. (See here for elaboration on this point specifically as to foreign affairs).
Posted at 6:02 AM