Federal Reserve Supreme Court Lisa Cook.

The Supreme Court for the past year has repeatedly allowed President Donald Trump to fire heads of independent agencies, but it appears to be drawing a line with the Federal Reserve. The court has signaled for months that it sees the Fed in a different light. It has said that the president can fire directors of other agencies for any reason, but can remove Fed governors only “for cause.” That is now being put to the test in a case involving Trump’s attempt to remove Fed governor Lisa Cook. On Wednesday during oral arguments, the Supreme Court seemed inclined to keep Cook in her job. But it largely skirted a key issue: What, exactly, is the legal principle that protects the Fed, but not the other agencies?