Presidential Tariff Authority Expands Beyond Steel and Aluminum

Why It Matters

The Trump administration has used Section 232 of the Trade Expansion Act of 1962 to impose sweeping tariffs on steel, aluminum, and a growing list of derivative products, all justified on national security grounds. A new Congressional Research Service report on Section 232 tariffs on steel and aluminum documents how that authority has been stretched, layered on top of separate tariff regimes, and expanded to new commodities. The result is a complex and escalating trade policy tariff landscape that is generating retaliation from major U.S. trading partners and drawing scrutiny on Capitol Hill.

The Big Picture

Section 232 of the Trade Expansion Act gives the President authority to restrict imports when the Secretary of Commerce determines they threaten to impair U.S. national security. The report traces how that authority has been applied and expanded through a series of presidential proclamations.

A February 2025 proclamation raised aluminum tariffs from 10 to 25 percent, eliminated all country exemptions for both steel and aluminum effective March 12, 2025, and broadened the list of derivative products subject to the tariffs. Since June 2025, the U.S. has imposed 50 percent tariffs on steel, aluminum, and derivative products from nearly all trading partners.

Proclamation 11021 introduced further changes on April 2. The administration shifted how tariffs are calculated, moving from the declared metal content value of an imported product to its full customs value. That methodological change alone significantly increases the effective cost of a wide range of manufactured goods. The proclamation also removed certain derivative products from Section 232 coverage entirely, simplified compliance requirements for some importers, and added copper to the framework alongside steel and aluminum.

U.S. Trade Representative Jamieson Greer, testifying before the House Ways and Means Committee, said the exclusion of some derivatives and simplified compliance rules in the April 2026 proclamation "could benefit some U.S. manufacturers" by reducing their input costs. The White House has asserted that the April 2026 changes "strengthen the tariffs and more effectively protect U.S. national security."

The Section 232 tariffs also interact with a separate layer of trade restrictions. Products covered under Section 232 are exempt from the global tariffs imposed under the International Emergency Economic Powers Act (IEEPA), but those tariffs still apply to the non-steel, non-aluminum content of derivative products. That creates a compliance environment that the report characterizes as layered and complex for importers.

Section 232 is different from the International Emergency Economic Powers Act (IEEPA), a 1977 law granting the president power to regulate international commerce only after declaring a national emergency in response to a foreign threat, according to the Council on Foreign Relations. Though the Trump administration imposed tariffs in 2025 using the IEEPA, the Supreme Court ruled in February 2026 that the law doesn't grant the president authority to levy tariffs.

Partner Retaliation

Canada has imposed 25 percent tariffs on approximately C$15.6 billion (roughly $11 billion USD) worth of U.S. steel and aluminum exports. The European Union voted to reimpose previously suspended retaliatory tariffs, though it suspended them temporarily through 2026 pending the outcome of U.S.-EU negotiations. The United Kingdom received some Section 232 relief as part of a May 2025 bilateral deal, illustrating how these tariffs are functioning as leverage in broader trade negotiations. That same dynamic is set to intensify ahead of the mandatory United States-Mexico-Canada Agreement (USMCA) review scheduled for July 2026. The CRS report notes that Section 232 tariffs were a central issue during USMCA negotiations in Trump's first term, and the question of whether to maintain, eliminate, or carve out exemptions for USMCA-compliant steel and aluminum from Canada and Mexico is likely to resurface.

Political Stakes

For the Administration

The tariff expansion represents a core pillar of its trade agenda, framed as a national security and economic sovereignty issue. The White House justification rests on the argument that domestic steel and aluminum production is strategically vital, and that import competition undermines it. The addition of copper to the Section 232 framework signals that the administration may be willing to extend this authority further still.

For Republicans

Particularly for those representing manufacturing districts, the tariffs offer a political argument about protecting domestic industry. But the downstream costs are real. Industries that use steel, aluminum, and copper as inputs, including auto manufacturing, construction and consumer appliances, face higher costs under the expanded tariff structure, particularly given the shift to full customs value assessment.

For Democrats

The party has historically supported protections for domestic manufacturing workers, but the retaliatory tariffs from Canada and the EU create friction with allies and raise costs for consumers. The administration's use of a national security justification to impose broad trade restrictions also raises questions about the scope of executive authority that some Democrats have flagged.

For the Public

The impact is most likely to be felt through prices. The shift to taxing full customs value rather than just metal content means the tariff burden increases on a wider range of finished goods, potentially passing costs along to consumers and businesses alike.

The Bottom Line

The CRS report makes clear that Section 232 tariffs on steel and aluminum have moved well beyond their original scope. What began as targeted measures on raw metals now covers an expanding list of derivative products, applies to nearly all trading partners at rates as high as 50 percent, and has been extended to copper. The methodological shift to full customs value assessment in April 2026 significantly amplifies the economic reach of these tariffs.

With the USMCA review approaching in July 2026 and retaliatory measures already in place from Canada and potentially the EU, Congress faces a decision point. The Ways and Means Committee hearings suggest lawmakers are not simply deferring to the executive on this.

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