Why Section 301 probes matter — and what they mean for Trump's tariffs

Here's CNBC's brief guide to Section 301s — what they are, why the White House has resorted to using them, and what President Donald Trump's administration hopes to achieve.

Put simply, Section 301 of the Trade Act of 1974 enables the investigation of perceived unfair trading practices to determine whether "the acts, policies, or practices of a foreign country are unreasonable or discriminatory and burden or restrict U.S. commerce."

The Office of the United States Trade Representative's (USTR) Jamieson Greer announced a series of new investigations on Wednesday targeting 16 trading partners, ranging from Singapore and Switzerland, to India and Norway. A full list is here.

Section 301 investigations are not new, with several probes into Brazil and China ongoing. The first Trump administration investigated foreign trade practices under Section 301 six times, with two probes into China and the EU resulting in the imposition of tariffs. Former President Joe Biden's administration also carried out Section 301 probes.

The latest investigations will examine whether these acts, policies, or practices burden or restrict U.S. commerce, and what action, if any, should be taken.

If the probes find against the economies in question, the USTR has the authority to impose new tariffs or other import restrictions, which could emerge in the summer.

The trade agency could also withdraw or suspend trade agreement concessions, or reach deals with the economies in question if they agree "to either cease the conduct in question or compensate the U.S.," USTR said.

Retaliatory action should "affect goods or services of the foreign country in an amount that is equivalent in value to the burden or restriction being imposed by that country on" U.S. commerce, it added.

The Section 301 probes follow the U.S. Supreme Court ruling that the Trump administration's "reciprocal" tariffs — imposed on a raft of trading partners in April 2025 under the International Emergency Economic Powers Act 1977 — were unlawful.

That left the administration scrabbling for other ways to reimpose duties that were struck down.

The White House initially responded to the Supreme Court's ruling by imposing a temporary 10% "universal" tariff (and threatening a higher 15% levy, which could be implemented soon) on all imported goods by using Section 122 of the Trade Act of 1974.

These tariffs are only temporary, however, and Trump has made no secret of wanting to find a way to restore tariffs that were disallowed.

The latest Section 301 investigations relate specifically to "structural excess capacity and production in manufacturing sectors", amid claims that rival economies are "dumping" excess production on U.S. markets and threatening domestic manufacturers.

USTR noted Wednesday that such practices pose a "serious challenge" to Trump's reindustrialization efforts and make it harder "to re-shore critical supply chains and create good-paying jobs for American workers."

The U.S. blames these dynamics for persistent trade deficits with trading partners, and for hampering growth.

"The United States will no longer sacrifice its industrial base to other countries that may be exporting their problems with excess capacity and production to us," Greer said Wednesday

Consultations will now take place with the economies whose trade practices are in the spotlight. The USTR will hold a public hearing covering each investigated economy starting on May 5. 

"After all of that, the USTR, we will have our findings and our analysis, and we will propose, if necessary, a responsive action," Greer said. "Responsive action can take a number of forms. It can be tariffs, it can be fees on services, it can be other things," he said.

China and the EU are among the economies who have pushed back against the probes, warning that trade deals reached with Washington over the past year could be jeopardized.

Greer is due to announce on Thursday another Section 301 probe investigating imported goods made using forced labor.

Analysts say the timing of the latest trade probes is curious, given the White House's focus on the ongoing military operation against Iran. Using Section 301 is seen as an overt attempt to resurrect Trump's global tariffs strategy, which is currently subject to time restrictions, with temporary duties due to expire in July.

"The timing is curious. You would think that the U.S. administration has got its hands full right now, but apparently not, " John Woods, Asia chief investment officer at Lombard Odier, told CNBC on Thursday.

Section 301 "will be essentially a proxy for the trade tariffs that hitherto were imposed but subsequently blocked by the Supreme Court," he said, adding that the U.S. would use the investigations as leverage for further negotiations over trade deals.

Goldman Sachs' Tim Moe said it's no surprise that the Trump administration is resorting to using Section 122 and Section 301s to target trade partners after the Supreme Court decison.

"It should not be a total surprise that this has been announced. The timing, of course, is always unexpected, but I think it should not be a total surprise. That's number one. Number two is that Section 301 requires a process; there has to be an investigation, and there's got to be factual developments ... [so] this will take some time to to play out.