The U.S. Supreme Court on Wednesday confronted a defining question of presidential authority as justices from across the ideological spectrum challenged the legality of President Donald Trump’s sweeping tariffs, a policy that has reshaped global trade and tested the limits of executive power.

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Solicitor General D. John Sauer, representing the Trump administration, faced sharp questioning over whether Trump had exceeded his authority by invoking a 1977 emergency law to impose wide-ranging tariffs on nearly every U.S. trading partner. Both conservative and liberal justices appeared skeptical that the law — the International Emergency Economic Powers Act (IEEPA) — granted the president such broad economic control.

At issue is whether Trump’s use of IEEPA to justify tariffs of unlimited scope and duration amounts to an unconstitutional overreach into Congress’s core powers to levy taxes and regulate commerce. Lower courts have previously ruled against the administration, concluding that Trump’s expansive interpretation of the statute violated both the letter and intent of the law.

Executive Power Under Scrutiny

Chief Justice John Roberts questioned whether Trump’s tariff regime encroached on congressional authority, noting that “the imposition of taxes on Americans has always been the core power of Congress.” Justice Amy Coney Barrett similarly pressed Sauer on whether the phrase “regulate importation” in IEEPA has ever historically been used to justify imposing tariffs.

Justice Elena Kagan emphasized that the power to impose taxes and regulate trade “has always been quintessentially legislative,” while Justice Ketanji Brown Jackson argued that Congress’s intent in passing IEEPA was “to constrain, not expand, presidential power.”

Even conservative Justice Neil Gorsuch voiced concern that allowing Trump’s interpretation to stand could result in a “one-way ratchet toward the continual accretion of power in the executive branch.”

The Major Questions Doctrine

The Court’s deliberations also centered on the “major questions doctrine,” which requires that any executive action of vast economic or political impact be explicitly authorized by Congress. Sauer argued that the doctrine does not apply in the realm of foreign affairs, but Roberts countered that the tariffs’ domestic tax implications place them squarely within congressional jurisdiction.

Neal Katyal, representing the coalition of businesses challenging the tariffs, said it was “simply implausible” that Congress intended to hand the president “the power to overhaul the entire tariff system and the American economy in the process.”

Billions at Stake, Trade War in Motion

Since being imposed, the IEEPA-based tariffs have generated an estimated $89 billion in revenue, according to U.S. Customs and Border Protection data. The administration insists that even if the Supreme Court strikes down Trump’s use of IEEPA, the tariffs will remain in place under other legal authorities.

The stakes extend far beyond domestic law. Trump’s aggressive use of tariffs has ignited a global trade war, rattling financial markets, alienating U.S. allies, and injecting volatility into global supply chains. The former president has used tariffs both as leverage in trade negotiations and as punishment for political disputes — targeting nations from China to Canada and India.

Historically, IEEPA has been used to freeze foreign assets or sanction hostile governments, not to levy import taxes. Critics warn that Trump’s approach, if upheld, could transform the emergency powers statute into a tool for unilateral economic policymaking.

A Defining Constitutional Test

The Supreme Court’s eventual ruling will carry sweeping implications for the balance of power between Congress and the presidency — and for the stability of global trade.

With a 6–3 conservative majority, the Court has in recent months sided with Trump in several emergency cases, allowing controversial policies to move forward while legal challenges proceed. Yet the intensity of Wednesday’s questioning suggests unease about expanding executive authority further.

A decision is expected in the coming months, though the administration has asked the Court to move quickly given the economic stakes.

If the justices side with Trump, future presidents may gain near-limitless control over trade policy through emergency declarations, potentially reshaping U.S. economic governance for decades to come.