While President Trump was at the World Economic Forum in Davos, Switzerland, reiterating his desire to control Greenland and hashing out a deal with the European nations that oppose that move, the U.S. Supreme Court was considering another of the president’s recent fixations.

Trump has been determined to fire Fed governor Lisa Cook from her post since August. He wrote on Truth Social that he was firing her “for cause” over allegations of mortgage fraud. She denied those allegations—but even more crucially for the country, noted that the president does not have the authority to fire a governor from the Fed, which is independent from the administration. (Presidents can remove Fed officials “for cause,” but Trump’s unproven allegations did not meet that standard, she said.) She filed a lawsuit in the U.S. District Court for the District of Columbia.

The Trump administration appealed, arguing as part of their appeal that the president’s decision shouldn’t be subject to judicial review. Allowing a broad definition of the “for cause” standard would essentially undermine the Fed’s independence, Cook’s attorneys argued. Meanwhile, Trump has continued to go up against Fed chair Jerome Powell, threatening a criminal indictment—which Powell called “a consequence of the Federal Reserve setting interest rates based on our best assessment of what will serve the public, rather than following the preferences of the President.” Trump has been musing about who he will pick to replace Powell as Fed chair when his term is up later this year.