The $370 Billion Supreme Court Gamble: Section 301 Tariffs Face Their Biggest Legal Test

The tariffs you've been paying on Chinese imports since 2018 might not be legal. A Supreme Court petition filed in February argues USTR never had the authority to expand Section 301 tariffs tenfold — and if the Court agrees, you could be looking at refunds on seven years of duties. Here's the timeline, the odds, and what you should be doing right now.

On February 20, 2026, something remarkable happened. The same day the Supreme Court struck down IEEPA tariffs as unconstitutional, a group of importers led by HMTX Industries filed a petition asking that same Court to review the legality of the original Section 301 tariffs on China. The timing wasn't coincidental — it was a message: if IEEPA falls, Section 301 should be next.

The stakes are staggering. Lists 3 and 4A alone cover approximately $320 billion in annual imports from China. Since 2018, importers have paid 25% on List 3 goods and 7.5% on List 4A goods — totaling hundreds of billions in cumulative duties. If the Supreme Court takes the case and rules for importers, the refund exposure could dwarf anything the trade community has ever seen.

But there's a clock ticking. If the Court doesn't schedule the case by June 25, 2026, it won't be heard until the fall term begins in October. And while importers wait for the Court, USTR just launched its second four-year review of Lists 1 and 2, with a comment deadline of July 5. Two fronts. One summer. Everything in play.

The Case: HMTX Industries v. United States

HMTX Industries LLC v. United States (Docket No. 25-1012) is the test case for over 4,000 importers who challenged the Section 301 tariffs in the Court of International Trade (CIT). The core legal question is deceptively simple: does the U.S. Trade Representative's authority to "modify" an existing tariff action allow it to expand that action by a factor of ten?

Here's the backstory. In 2018, USTR imposed Section 301 tariffs on China in waves:

Lists 1 and 2 were part of the original Section 301 investigation. Nobody seriously disputes USTR's authority to impose those. But Lists 3 and 4A? Those were added later as "modifications" under Section 307(a)(1)(C) of the Trade Act of 1974 — a provision that allows USTR to modify an action when "the burden or restriction on United States commerce... has increased or decreased."

The plaintiffs' argument is straightforward: Congress gave USTR the power to tweak existing tariffs, not to create entirely new ones covering thousands of additional products. Going from $50 billion to $370 billion isn't a "modification" — it's a new trade action that should have required a new investigation.

The Federal Circuit's Ruling

In September 2025, the U.S. Court of Appeals for the Federal Circuit sided with the government in a decision that divided the trade law community. The court held that Section 307(a)(1)(C) "independently authorized" USTR to implement Lists 3 and 4A because China's retaliation against Lists 1 and 2 constituted an increased burden on U.S. commerce.

The court's logic created what critics call an "escalation ratchet" — China retaliates, which increases the burden on U.S. commerce, which authorizes more tariffs, which provoke more retaliation, which authorize more tariffs. Under this interpretation, a single Section 301 investigation could theoretically justify tariffs on every product imported from China.

The Federal Circuit also addressed whether USTR properly considered public comments, finding that the agency's decision to publish proposed modifications in the Federal Register and review public comments — even if done somewhat informally — satisfied the Administrative Procedure Act. The trial court had previously found USTR's notice-and-comment process inadequate, but the Federal Circuit reversed on remand.

Why the Supreme Court Might Take This Case

The certiorari petition makes three arguments for why the Court should grant review:

1. No percolation possible. All challenges to Section 301 actions must go through the CIT and Federal Circuit — there's no circuit split possible, so the Supreme Court is the only body that can correct the Federal Circuit's interpretation.

2. Massive practical significance. With IEEPA struck down, Section 301 is now the administration's primary statutory tool for imposing tariffs. The petition notes that the administration has "repeatedly stated that it plans to rely more heavily on Section 301" — making the scope of that authority a live, urgent question.

3. Textual argument is strong. "Modify" has a well-established meaning in administrative law. The Supreme Court has previously held (in MCI Telecommunications v. AT&T, 1994) that "modify" means incremental change, not fundamental transformation. A tenfold expansion strains any ordinary reading of the word.

Only four justices need to vote "yes" at conference for the Court to take the case. Given the current Court's interest in constraining agency authority — demonstrated by decisions like Loper Bright overturning Chevron deference — the odds of cert being granted are meaningfully higher than the typical 1-2% rate.

The June 25 Deadline: Why Timing Matters

The Supreme Court's current term ends in late June. For the HMTX petition to be heard during this term, it would need to be scheduled for conference by approximately June 25, 2026. The government's brief in opposition is due soon, and the Court typically considers petitions within a few weeks of briefing completion.

If the case isn't scheduled before the summer recess, it won't be conferenced until October at the earliest, with oral argument unlikely before early 2027 and a decision possibly not arriving until June 2027. For importers currently paying 25% on List 3 goods, that's another 12-18 months of duties that may or may not be refundable.

The practical implication: if you import goods on Lists 3 or 4A, you need to be preserving your rights now — not after the Court announces whether it will hear the case.

The Second Four-Year Review: Lists 1 and 2 Under the Microscope

While the Supreme Court decides whether Lists 3 and 4A are legal, USTR is simultaneously conducting its second statutory four-year review of Lists 1 and 2. On May 6, 2026, USTR published a Federal Register notice initiating the review process for the two actions that became effective July 6, 2018, and August 23, 2018.

The four-year review isn't about legality — it's about whether the tariffs are still achieving their trade policy objectives. Under Section 307(c) of the Trade Act, tariffs automatically terminate after four years unless USTR determines they should continue. The first four-year review (concluded in May 2024) not only kept all tariffs in place but increased rates on $18 billion worth of goods in strategic sectors.

Key deadlines for the second review:

Domestic industry representatives who benefit from the tariffs must submit requests for continuation via the USTR portal at comments.ustr.gov. If no domestic industry requests continuation, the tariffs could theoretically expire — though given the current political climate around China trade, that outcome is vanishingly unlikely.

What This Means for Your Import Operation

The convergence of these two proceedings creates a rare strategic moment for importers of Chinese-origin goods. Here's why:

If the Supreme Court grants certiorari and eventually rules for importers, duties paid on Lists 3 and 4A goods since 2018 could be refunded. We're talking about seven years of 25% and 7.5% duties on $320 billion in annual trade. Even a fraction of that represents enormous exposure.

If the Court denies cert, the Federal Circuit's interpretation stands permanently. Section 307's "modify" authority becomes essentially unlimited, and future administrations can expand any Section 301 action without conducting a new investigation.

If the four-year review results in modifications, List 1 and 2 tariff rates could change — up or down — by early 2027. The first review raised rates on semiconductors, batteries, EVs, and medical equipment. The second review could target additional sectors.

What You Should Do Right Now

1. Preserve your protest rights on Lists 3 and 4A entries. If you're importing goods subject to List 3 (25%) or List 4A (7.5%) tariffs, ensure you're filing timely protests on liquidated entries. If the Supreme Court ultimately rules these tariffs unlawful, only importers with preserved claims will be eligible for refunds. The 180-day protest window is unforgiving.

2. Audit your HTS classifications against the Section 301 lists. The four-year review is an opportunity to identify whether your products are correctly classified — and whether a reclassification might move them off a covered list. With ~5,700 HTS codes on List 3 alone, classification accuracy is the difference between 25% duty and zero.

3. Submit comments in the four-year review if you benefit from List 1/2 tariffs. Domestic manufacturers who benefit from the tariffs must affirmatively request continuation by July 5, 2026. If you're on the flip side — an importer harmed by the tariffs — monitoring which industries request continuation can inform your sourcing strategy.

4. Model your refund exposure. Calculate total duties paid on List 3 and 4A entries since 2018. If the Supreme Court grants cert, the case value calculation becomes critical for budgeting, insurance, and supply chain decisions. Know your number.

5. Watch the conference calendar. The Supreme Court posts its conference schedule publicly. When HMTX v. United States appears on the conference list, you'll have approximately two weeks' notice before the cert decision drops.

What's Coming Next

The next 60 days are pivotal:

• Late May / Early June 2026: Government's brief in opposition to certiorari due
• June 2026: Potential conference scheduling for HMTX petition
• June 25, 2026: Approximate last date for the case to be conferenced this term
• July 5, 2026: Comment deadline for List 1 four-year review
• October 2026: If not taken this term, case moves to October Term 2026

Meanwhile, the administration's new Section 301 investigations targeting 76 countries (covering overcapacity and forced labor) continue advancing toward implementation. The legal framework established by HMTX — however the Court rules — will directly shape how far those new tariffs can reach.

The Bigger Picture

Seven years into the Section 301 tariffs on China, the legal architecture supporting them is being tested from every angle — courts, statutory review, and the political reality of a trade landscape that looks nothing like 2018. The importers who preserved their rights from the beginning are now positioned for potentially enormous refunds. Those who didn't are watching from the sidelines.

Whether you're paying 25% on List 3 furniture and electronics or 7.5% on List 4A consumer goods, the next few months will determine whether those rates are permanent features of your cost structure or seven-year anomalies that get unwound. TariffLens can help you identify exactly which of your products sit on challenged lists and model your exposure — but the window to act is narrowing.

This article is for informational purposes only and does not constitute legal, tax, or customs advice. Consult a licensed customs broker or trade attorney for guidance specific to your situation.