The Constitution states that Congress has the power to "lay and collect Taxes, Duties, Imposts and Excises, to pay the Debts" of the federal government. Indeed, in order to emphasize the location of this power in the Congress, the Constitution also requires that all legislation "for raising Revenue shall originate in the House of Representatives."

So, if only Congress can impose taxes, how can the president impose tariffs?

Here is the backstory.

However one characterizes a tariff, since it consists of the compulsory payment of money to the federal government, it is a form of taxation. It is — to use James Madison's language — a duty or an impost. The federal government survived on duties and imposts — some of which were imposed on the states — from the time of its creation in 1789 until the War Between the States. Even under Abraham Lincoln, when unconstitutional income taxes were imposed, they were done by legislation, not executive fiat.

Then came Franklin D. Roosevelt and a congressional ban on the exportation of armaments to be implemented at the president's discretion. This sounds fairly benign, yet it fomented the supercharged presidency that we have today. When Congress banned the sale of American arms to foreign countries, it did so by giving FDR the power to decide what to ban and upon which countries to impose the ban. Then it did the unthinkable: It made a violation of the president's fiats a federal crime.

I call this unthinkable because under the Constitution's Due Process Clause jurisprudence, at the federal level only Congress can make behavior criminal.

In defiance of FDR's ban, Curtiss-Wright Export Corporation, an American manufacturer of military hardware, sold armaments to the government of Bolivia, and the Department of Justice persuaded a federal grand jury to indict the corporation. Then a federal judge dismissed the indictment on the constitutional basis that only Congress can decide what behavior is criminal and it cannot give that power to the president.

The trial court merely enforced the well-known and universally accepted non-delegation doctrine. It stands for the principle that the three branches of government cannot delegate away any of their core powers. Among Congress' core powers is writing laws and deciding what behavior is criminal. By giving away this power to the president, the trial court ruled, Congress violated the non-delegation principle, and thus FDR's determination that arms sales to Bolivia was criminal was itself a nullity.