This Wednesday, Nov. 5, the Supreme Court will hear arguments in what President Donald Trump called “one of the most important cases in the history of our country.” Trump is not wrong in suggesting that the U.S. Supreme Court will decide the significant question of constitutional jurisdiction while answering the question—who controls U.S. trade policy — Congress or the president?

The plaintiffs in Learning Resources v. Trump, are asking the Supreme Court to uphold lower federal court rulings in two separate cases that found that Trump did not have the legal authority to impose so-called reciprocal tariffs on imported goods from nearly every country in the world, along with separate “fentanyl tariffs” on China, Mexico, and Canada.

Trump’s current tariffs range from a baseline of 10% on many countries to as high as 50% on imported goods from Brazil and India.

The legal controversy centers on Trump’s use of the International Emergency Economic Powers Act (IEEPA) after Trump issued a series of executive orders back in Feb. imposing tariffs using this statute.

SCOTUS blog offers an excellent explanation of the International Emergency Economic Powers Act of 1977 (IEEPA): “Congress gave presidents sweeping powers to deal with any ‘unusual and extraordinary threat with respect to which a national emergency has been declared.’ Specifically, when the president declares such an emergency, he then has the power to (among other things) ‘investigate,’ ‘regulate,’ or ‘prohibit’ imports. The word ‘tariff’ or ‘tax’ does not appear in the statute, but the administration argues that the president’s power to “regulate” such trade includes the power to impose tariffs on it.”

Two lower courts have already rejected Trump’s interpretation. The challengers—a coalition of conservative, small businesses including toymakers and wine importers—argue that Trump has usurped Congress’s constitutional power to tax.

U.S. District Judge Rudolph Contreras ruled for Learning Resources and hand2mind, agreeing with them that “the power to regulate is not the power to tax.” 

The other case was brought in the U.S. Court of International Trade by several small businesses, including V.O.S. Selections, a New York wine importer, and Terry Precision Cycling, which sells women’s cycling apparel. Terry describes the tariffs as “an existential threat” to the company. It was joined with a second case, also filed in the Court of International Trade, brought by 12 states, which say that they are affected by the increased tariffs because they buy goods from overseas directly and purchase products that were imported by others.

On May 28, a panel of judges at the US International Court of Trade unanimously ruled that the IEEPA tariffs were illegal.

Stanford Law Professor Michael McConnell, a former appellate judge representing the plaintiffs, frames the issue starkly telling the Stanford Legal podcast: “Tariffs are taxes. Taxes on Americans. The tax bill goes to my clients. My clients pay the bill. Tariffs are not paid by foreign governments as President Trump sometimes says. Taxes on American citizens is something that is closely guarded by Congress. We actually fought the American Revolution largely on the slogan of no taxation without representation. That is to say you shouldn’t have to pay taxes unless you’re represented in a legislative body that enacts them.”

Article I, Section 8 of the U.S. Constitution gives Congress the power to tax and regulate commerce. The Supreme Court’s decision will either validate the unprecedented expansion of presidential economic authority imposed by Trump or reaffirm Congress’s constitutional role as the sole body empowered to impose taxes on the American people.

Conservative columnist George Will describes the case in front of SCOTUS with: “This momentous case must either undermine or buttress the Constitution’s architecture: the separation of powers.”

For this part, Trump says that if he loses the case, “we will be a weakened, troubled, financial mess for many, many years to come” and that “we’d have to pay back money” and reimburse companies for the billions of dollars they have already paid. 

The decision in front of the Supreme Court will be a test on executive branch power and whether Congress should continue to “have power to lay and collect taxes, duties, imposts, and excises” as laid out by the Constitution of the United States.