President Donald Trump on Thursday announced tariffs on polysilicon and its related products, in his administration’s latest attempt to eliminate China’s choke points in the global supply chain for solar panels and semiconductors.

But Trump’s directive won’t take effect until Dec. 4 — well after November’s midterm elections and a planned September summit between Trump and Chinese leader Xi Jinping — as the administration grapples with voters complaining of high prices and fragile trade negotiations with China.

“This will bring the supply chain here,” Commerce Secretary Howard Lutnick said of the order on Thursday alongside Trump at the White House. “We’ve got the industry here, it’s too small, and it’s going to explode.”

Because polysilicon is used in semiconductors and solar panels, it’s essential for military hardware and everyday electronics like cell phones and laptops, in addition to the world’s fastest-growing energy source.

The order imposes a 15 percent tariff on imported polysilicon and its derivatives, as well as minimum prices for imports of polysilicon, polysilicon ingots and wafers, solar cells and solar modules.

It also includes a clause intended to prevent companies from stockpiling those materials between now and December, authorizing Customs and Border Protection to restrict imports if it suspects an importer is attempting to dodge the higher duties.

Trump’s order is the result of a Commerce Department investigation launched last July into national security risks in the polysilicon supply chain, as part of a broader effort to shift supply chains away from China for multiple industries including wind turbines and robotics.

China has a near-monopoly on the production of polysilicon, according to S&P Global. But recent U.S. efforts to limit key areas of trade with China have already drawn a backlash from Beijing, which earlier this week implemented new controls on drone exports to the U.S.

The White House emphasized the order’s impact on domestic semiconductor production, a key focus as the U.S. looks to build out infrastructure related to artificial intelligence. Trump said the U.S. will “have a big percentage of the chip business by the time I leave office.”

But Thursday’s order may have a big impact on the solar industry, according to Jon Toomey, president of the pro-tariff Coalition for a Prosperous America organization.

“This proclamation delivers the most significant global trade protection action for the American polysilicon and solar industry in the modern era,” Toomey said in a statement. “For the first time, the United States is protecting the entire solar supply chain with a single action — and rewarding the manufacturers that build here — while taking a significant step to bolster the domestic semiconductor supply chain.”

A group of 25 Democratic-led states sued President Donald Trump’s administration Monday to block the latest round of tariffs imposed on goods from dozens of countries.

The lawsuit in the U.S. Court of International Trade marks the latest in a growing list of legal actions that accuse the White House of exceeding its authority when it used Section 301 of the Trade Act of 1974 — which allows a president to impose tariffs over unfair trade practices — to penalize countries over the alleged use of forced labor after prior trade penalties had either expired or been invalidated by the Supreme Court.

“The Plaintiff States oppose forced labor in all its forms and support protections for workers around the globe,” the states said in their lawsuit. “But the Administration cannot use forced labor as a pretext to continue its illegal tariff scheme.”

Monday’s complaint contests tariffs of 10 or 12.5 percent the administration slapped on goods from 60 economies, including China and the European Union, that took effect last month.

“President Trump is so intent on raising the cost of living for Americans that he is willing to break law after law after law to do so,” said California Attorney General Rob Bonta, whose state is among the plaintiffs, in a statement announcing the lawsuit.

“Tariffs are taxes,” Bonta said. “And the American people cannot and should not shoulder the extra costs that come from the President’s failed and illegal economic policy — no matter how much the President wants them to.”

The effort to block Trump’s third crack at rebuilding his global tariff regime comes after the Supreme Court in February knocked down tariffs the president imposed on countries under the 1977 International Emergency Economic Powers Act, and after the Court of International Trade ruled in May that the Section 122 surcharge Trump imposed in their place was also illegal. The trade court’s May ruling was stayed, allowing the duties to keep being collected pending appeal. Those tariffs expired last month.

The White House defended the tariffs, saying the administration was using its “lawful authority” to crack down on practices that burden American commerce.

“A foreign country’s failure to impose and effectively enforce a prohibition on the importation of goods produced with forced labor is unreasonable and burdens U.S. commerce, including American workers, and must be addressed,” White House spokesperson Kush Desai said in a statement. “Section 301 tariffs have proven to be a legally durable tool since the President’s first term, and they remain so now.”

The lawsuit also accuses the U.S. of bypassing country-specific consultations and failing to explain why duties on countries with such varied forced-labor measures were set in a “nearly uniform manner.”

And it comes on the heels of lawsuits from two groups of small businesses that challenged the tariffs the day they took effect: one led by Burlap & Barrel, a New York spice importer, and a separate suit led by Learning Resources, an educational-products maker that was the named plaintiff in the Supreme Court case that invalidated Trump’s IEEPA tariffs.

Background: The dispute centers on Trump’s use of Section 301, an authority widely viewed as far more legally durable than the other powers Trump tapped to impose tariffs.

Duties from one Section 301 investigation into China during Trump’s first term have now lasted more than seven years. But Section 301’s durability does not give the president unlimited discretion, because the law requires the USTR to identify specific foreign acts, policies or practices and show that they burden or restrict U.S. commerce.

Matthew Seligman, founder of Grayhawk Law and an attorney representing importers seeking tariff refunds, said the states’ challenge is strong but faces a harder legal path than the challenges to the IEEPA and Section 122 tariffs.

“Unlike those prior cases, this case will turn on how much the courts defer to the administration’s seemingly pretextual rationalization that these tariffs are aimed at combatting forced labor,” Seligman said.

“Typically, courts grant substantial deference to the executive branch about these sorts of policy judgments — especially when it implicates foreign affairs —but, as is so often the case with the Trump administration, this case will really test the limits of that judicial deference,” he added.