The Office of the U.S. Trade Representative, led by Jamieson Greer, launched two sweeping sets of trade investigations in March 2026 under Section 301 of the Trade Act of 1974, covering a combined total of more than 76 economies and targeting two distinct trade practices: government-subsidized manufacturing overcapacity and the failure to ban imports made with forced labor. The first set of probes, announced March 11, targeted 16 economies — including China, the European Union, Mexico, Japan, South Korea, Vietnam, Taiwan, Malaysia, India, and several others — for excess industrial capacity in sectors including steel, automobiles, batteries, semiconductors, solar panels, chemicals, and industrial machinery. CNBC confirmed the probes on March 11, and NPR reported that China slammed the investigations as a "pretext for political manipulation." The second set, announced March 13, targeted 60 economies for allegedly failing to enforce bans on goods made with forced labor.

The investigations are widely understood in trade legal circles as a "Plan B" for imposing tariffs on U.S. trading partners after the Supreme Court ruled 6-3 on February 20 that IEEPA — the International Emergency Economic Powers Act — does not authorize tariffs. That ruling invalidated the Trump administration's primary legal mechanism for imposing broad reciprocal tariffs on most U.S. trading partners, forcing the administration to pivot to alternative statutory authorities. Section 301 of the Trade Act of 1974 allows tariffs to be imposed if a formal investigation finds that a trading partner's acts, policies, or practices are unreasonable, discriminatory, or burden U.S. commerce. Unlike IEEPA-based tariffs, Section 301 tariffs are not time-limited or capped at a specific rate, and they survived a prior Supreme Court challenge during Trump's first term. CNBC explained on March 12 that the investigations could "pave the way for new tariffs" that have stronger legal footing than the struck-down IEEPA measures.

The process will proceed over several months. Written comments from interested parties were due by April 15, 2026, with public hearings on the forced labor investigations beginning April 28 and hearings on the overcapacity investigations beginning May 5. USTR is expected to issue preliminary findings in late 2026 that could serve as the basis for new tariff rates. NBCNews confirmed the investigation scope and timeline and reported that Asian economies are "scrambling to respond," with Fortune noting that Malaysia, Vietnam, Thailand, and Cambodia are among the most exposed in the overcapacity probes given their role as manufacturing hubs for Chinese-designed products assembled to avoid earlier tariffs.

China's Commerce Ministry condemned the overcapacity investigations as "extremely unilateral, arbitrary and discriminatory, and a typical protectionist act," and a Chinese government economist warned in the Asia Times that Beijing could resume restrictions on rare earth element exports — which China dominates globally — if Washington proceeds with new tariffs under the probes. IAM Union, a major U.S. manufacturing workers' union, formally backed the USTR investigations in a statement, arguing they "target global overcapacity and forced labor" that directly harm American workers. The unusual combination of labor union support and business community skepticism reflects the split within traditional Democratic and Republican coalitions over trade policy.