Trump’s tariff powers to be tested by U.S. Supreme Court. What’s at stake?

The U.S. Supreme Court on Wednesday will hear arguments on whether U.S. President Donald Trump has authority to impose tariffs under emergency powers.

The U.S. Supreme Court on Wednesday will hear arguments on whether U.S. President Donald Trump has authority to impose tariffs under emergency powers — a case Trump has called “one of the most important” in the court’s history.

The case centres around Trump’s use of national emergency authorities to lay tariffs on countries around the world, including the so-called fentanyl tariffs on Canada, Mexico and China, as well as the “reciprocal” levies on dozens of other nations.

Trump has argued the tariffs are a “vital” negotiating tool to reach deals on trade and policy, and points to the rising revenues they are generating for a government facing a nearly US$38 trillion national debt.

Yet the state and small business plaintiffs, who say they’re facing economic harm from the extra costs on imports, have so far won support from lower courts that have ruled Trump overstepped his authority as president by ordering tariffs without approval from Congress.

Whether the nation’s highest court will uphold those rulings is an open question, lawyers and analysts say.

“It could go either way,” said Chi Carmody, a professor at Western University who studies international trade law.

Trump declared a national emergency on fentanyl in February to justify the economy-wide tariffs on Canada, Mexico and China, saying they were necessary to elicit action from those countries to curb the flow of the deadly opioid.

Those tariffs, now set at 35 per cent for Canada, do not apply to goods compliant with the Canada-U.S.-Mexico Agreement on free trade (CUSMA).