Trump's Legal Authority to Impose Tariffs
What happened to Congress?
In case you were wondering (as I have been wondering) how our president can simply snap his fingers and impose tariffs (of up to 25% on all goods) on imports from Mexico without even informing, let alone getting legal authorization from, Congress, an excellent essay by Scott Anderson and Kathleen Claussen over on Lawfare lays out the relevant legal framework.
The bottom line: while earlier instances of unilateral tariff impositions by the Trump Administration (on goods from China, on all steel and aluminum imports, etc.) were all premised on broad presidential authority granted in various trade-related statutes (e.g. Section 301 of the 1974 Trade Act), Trump is basing his power to impose the new Mexican tariffs (scheduled to go into effect on June 10) on "the authorities (sic) granted to me by the International Emergency Economic Powers Act (IEEPA)."
The IEEPA [full-text here] kicks in once a national emergency has been declared with respect to an "unusual and extraordinary threat … to the national security, foreign policy, or economy of the United States." The IEEPA then gives the president facing such emergency the power to:
regulate … or prohibit … any … transportation, importation, or exportation of … any property in which any foreign country or a national thereof has any interest … or with respect to any property, subject to the jurisdiction of the United States.
Though the IEEPA has apparently never been invoked before in connection with tariffs on imported goods, more typically being used for the imposition of economic sanctions or for freezing bank accounts, it does appear that such an action would fit within the scope of the statutory authorization (which has, as Anderson and Claussen explain, been given broad readings by the courts in the few cases in which it has been challenged). The President, you will recall, has declared a national emergency with respect to migrants at our southern border, and though Congress voted to rescind the emergency declaration, Trump vetoed the measure and there were not enough votes to override the veto.
The statute, though, does raise some tricky "delegation doctrine" questions; there are some limits to Congress' power to delegate its law-making functions to others (including members of the Executive Branch), though locating the line which Congress may not cross has proven, over the years, to be an enormously difficult enterprise.
But putting aside the constitutional questions, one has to hope that at some point Congress will return to its senses and re-assert its fundamental law-making powers by either repealing or, perhaps more sensibly, providing for a 15- or 30-day "sunset" provision that will nullify the presidential actions unless during that period Congress approves them via legislation, by majority vote in each chamber. There are certainly times, in the face of true national emergencies, when the Chief Executive has to act quickly and decisively; that is as true for economic warfare as for ordinary on the ground military warfare. But there is no good reason for allowing the president to entirely avoid the need (and the constitutional requirement) to obtain a majority of each house of Congress in order to declare economic war (or, for that matter, to declare ordinary war).
I suspect that because this issue is now seen as being all about Mr. Trump and is all entangled in the Trump/Anti-Trump miasma, there's probably no chance of any revision in the law until a new Chief Executive is in place. But one can still hope.