President Trump has raised or lowered tariffs/taxes, or he has threatened other nations that he will do so, on an almost daily basis since Inauguration Day. He does not have the legal authority to do so.
The U.S. Constitution authorizes the imposition of tariffs in the very first clause of Article I, Section 8, which famously grants Congress eighteen, and only eighteen, limited and enumerated legislative powers. That Clause provides that:
The Congress shall have Power To lay and collect Taxes, Duties, Imposts and Excises, to pay the Debts and provide for the common Defence and general Welfare of the United States; but all Duties, Imposts and Excises shall be uniform throughout the United States.
This provision stems from centuries of conflict in Great Britain (and the colonies) about the location of the power to tax, and from the American Revolutions rejection of Parliament's effort to impose "taxation without representation" on the colonies.
Samuel Johnson's 1755 Dictionary of the English Language defines a Duty as a "Tax; impost; custom; [or] toll." It defines an Impost as "a tax; a toll; [or] a custom paid." A tariff is either a "duty" or an "impost," and the power to impose such tariffs/taxes is therefore explicitly given to Congress, not the President, by the Constitution. From the Tariff Act of 1789, passed by the First Congress, to the Tariff of Abominations passed in 1828, to the Smoot-Hawley Tariff passed in 1930, it has always been understood that the Constitution gives only Congress the power to impose, raise, or lower tariffs, which are taxes. It does not give that power to the President.
Under case law going back to the nineteenth century, Congress can delegate some measure of power to the President to adjust tariff rates, but President Trump can only impose, raise, or lower tariffs if Congress has delegated that power to him by statute. J.W. Hampton, Jr. & Co. v. United States, 276 U.S. 394 (1928). He also can only do so as long as the delegation of power by Congress is guided by "an intelligible principle." This is a wise and good feature of our Constitution, a document which should be revered and followed, not trashed.





