The U.S. Supreme Court declined on June 15, 2026 to hear a challenge to Section 301 tariffs on Chinese imports, letting stand a lower court ruling that upheld the Trump administration's expansion of those duties from an original $50 billion in covered goods to $370 billion. For the HVAC industry, which sources a meaningful share of components, electronics, and finished products from China, the ruling closes off the last realistic path to overturning tariffs that have been in place for eight years across two administrations.
What was actually being litigated: The case, HMTX Industries v. United States, challenged the legal authority the U.S. Trade Representative used to expand the original Section 301 tariffs through 'List 3' and 'List 4A' — additional categories of Chinese goods added after China retaliated against the initial 2018 tariffs. The plaintiffs argued the expansion exceeded the procedural authority Congress granted under the Trade Act of 1974. The Federal Circuit Court of Appeals disagreed, and the Supreme Court's refusal to hear the case makes that ruling final.
Why this is different from the IEEPA tariff ruling: This decision should not be confused with the Supreme Court's February 2026 ruling that struck down many of the administration's 'Liberation Day' tariffs imposed under the International Emergency Economic Powers Act. That earlier ruling created genuine relief and uncertainty in a different part of the tariff landscape. The Section 301 China tariffs operate under different statutory authority and were never part of that case — they have remained in place continuously since 2018 regardless of what happened with IEEPA tariffs, and they remain in place now with no further legal avenue for reversal.
The practical effect on pending litigation: More than 3,500 companies filed lawsuits at the Court of International Trade seeking refunds on tariffs paid under Lists 3 and 4A, with those cases stayed pending the outcome of the Supreme Court petition. With certiorari denied, those cases are expected to be dismissed, closing off refund hopes for importers who were waiting on the litigation's outcome rather than pursuing other exclusion or refund mechanisms.
What this means for HVAC sourcing decisions: Section 232 tariffs on steel and aluminum and Section 301 tariffs on Chinese-origin goods are now both confirmed as durable features of the cost environment rather than temporary or legally vulnerable. For manufacturers and distributors who source components, control boards, motors, or finished equipment with Chinese content, the planning assumption should be that these costs are permanent unless and until Congress or a future administration changes the underlying policy — court challenges are no longer a live possibility.
The forward-looking risk: The ruling lands as the USTR is conducting expedited Section 301 forced labor investigations into more than 60 countries, with public hearings scheduled for early July and proposed tariffs of 10% to 12.5% under consideration. Industry watchers note this could effectively reconstitute tariff coverage that was previously imposed under the now-invalidated IEEPA authority, using Section 301's now-confirmed legal durability as the new vehicle. For HVAC manufacturers and distributors, the message from this ruling is that contesting these tariffs in court is no longer a viable strategy — sourcing diversification and pricing strategy are the only remaining levers.
