U.S. President Donald Trump speaks during an event to honor recipients of the Purple Heart in the East Room of the White House on August 07, 2025 in Washington, DC.

Anna Moneymaker | Getty Images

President Donald Trump on Friday warned U.S. courts against blocking his tariff policy, citing its “positive impact” on the stock market and saying such a move could cause a severe economic downturn.

“If a Radical Left Court ruled against us at this late date, in an attempt to bring down or disturb the largest amount of money, wealth creation and influence the U.S.A. has ever seen, it would be impossible to ever recover, or pay back, these massive sums of money and honor,” Trump wrote on his Truth Social platform Friday morning.

“It would be 1929 all over again, a GREAT DEPRESSION,” he added.

Trump’s comments come as a federal appeals court is hearing arguments on how to handle his tariff policy. Former House Speaker Paul Ryan told CNBC this week that the Supreme Court could end up disqualifying the duties that have been ordered under the International Emergency Economic Powers Act enacted by Congress in 1977.

“If they were going to rule against the wealth, strength, and power of America, they should have done so LONG AGO, at the beginning of the case, where our entire Country, while never having a chance at this kind of GREATNESS again, would not have been put in 1929 style jeopardy,” Trump said of the courts’ potential actions around tariffs. “There is no way America could recover from such a judicial tragedy.”

Legal challenges to the imposition of higher U.S. tariffs by the White House have centered on arguments that they may exceed emergency powers granted to the President by Congress in the 1970s. However, Alan Wolff, a senior fellow at the Peterson Institute for International Economics, said in a report this week that these levies being struck down would lead to a “massive amount of red tape” around who would receive refunds.

“This is a bell that cannot easily be fully unrung,” Wolff said.

Market impact

Trump said the tariffs have had a “huge positive impact” on the stock market. Markets this year have appeared to respond positively whenever the White House has dialed back on tariffs, and have reacted negatively when Trump has pressed the case for higher duties on imports to the U.S.

For example, when Trump suspended the initial “liberation day” tariffs in early April for the next 90 days, the Nasdaq Composite soared 7% in just a few minutes, with other major market averages also posting large gains that week. Since then, the market has seen specific sectors jump whenever Trump backed off targeted threats, such as those against semiconductor imports. Companies such as AMD and Marvell, as well as Apple, then posted solid gains with the duties granting broad exemptions to any company that announces plans to add manufacturing in the U.S.

The rallies, however, have often proven short-lived as the president has frequently changed gears on his tariff rhetoric. Markets lately have been more stable around tariff news, with investors viewing the president’s views as continuously subject to change.

— CNBC’s Jeff Cox and Scott Schnipper contributed reporting,