On March 3, the Supreme Court will hear a plea to invent a new rule of constitutional law with the potential to put an end to the republic the Constitution established, if not under President Trump, then under some despotic successor. This rule would end statutory protections for independent government officials resisting a president’s efforts to use his power to demolish political opposition and protect his party’s supporters. Elected strongmen around the world have put rules in place allowing them to fire government officials for political reasons and used them to destroy constitutional democracy and substitute authoritarianism. But these authoritarians never had the audacity to ask unelected judges to write such rules, securing their enactment instead through parliamentary acts or a referendum.

The blessings of liberty in this country and other functioning democracies depend in important ways on something that legal scholars call the “internal separation of powers.” Prosecutors in robust democracies, for example, enjoy some separation from the head of state, as they are expected to apply the law neutrally. In early America, prosecution was lodged outside of presidential control, among private citizens, state officials, and distant United States Attorneys. Electoral commissions and media regulators, here and …