The Supreme Court could end up ruling if Trump has authority under the International Emergency Economic Powers Act to impose universal duties on imports.

The U.S. Court of International Trade on Wednesday blocked steep reciprocal tariffs unilaterally imposed by President Donald Trump on scores of countries in April to correct what he said were persistent trade imbalances.

The ruling deals a potentially serious blow to the Republican president’s economic agenda and ongoing efforts to negotiate trade deals with various nations.

Dow futures jumped 500 points on news of the ruling, which the Trump administration immediately appealed to the U.S. Court of Appeals for the Federal Circuit.