The U.S. Supreme Court could throw a wrench into Trump’s plan to take Greenland as soon as Tuesday

The U.S. Supreme Court could rule on Tuesday that President Donald Trump’s trade tariffs are illegal—and that would throw up a significant hurdle for his plan to acquire Greenland.

President Trump posted his latest threat to take over Greenland late last night on Truth Social: “Now it is time, and it will be done!!!”

Previously, on Saturday, he threatened to impose tariffs of 10%, on Denmark, Norway, Sweden, France, Germany, the U.K., the Netherlands, and Finland, rising to 25% on June 1, “until such time as a Deal is reached for the Complete and Total purchase of Greenland.”

But analysts noted this morning that the court is due to issue rulings on Tuesday of this week. The expectation on Wall Street is that the court will rule that the president does not have the power under the International Emergency Economic Powers Act (IEEPA) to impose tariffs on routine international trade. If that happens, Trump’s threats could become meaningless, at least in the short-term.

“Threatened U.S. tariffs … may be overturned by the U.S. Supreme Court,” UBS advised clients in a note this morning.

At ING, Carsten Brzeski and Bert Colijn said, “If the Supreme Court rules against all earlier IEEPA tariffs, Trump’s latest announcement [about Greenland] would be void, and he would have to find other tariffs. Something that would take more time.”

The ruling had been expected earlier this month. The delay has caused some to speculate that the court, which at oral arguments appeared to be skeptical of the White House’s arguments, may now be leaning toward the Trump Administration. The court has a history of taking longer to produce its big, unexpected rulings.

“While the Court is positioned to issue additional opinions this week—sessions are scheduled for Tuesday and Wednesday—our economists’ expectation is that the ruling may not come until later in the year, potentially as late as June,” Jim Reid and his colleagues at Deutsche Bank said in their morning note.

This story was originally featured on Fortune.com