But other democracies provide a roadmap for courts to prevail over attacks from the executive branch. Just two months in, U.S. President Donald Trump’s administration is aggressively challenging judicial constraints on its power, risking a showdown—and constitutional crisis—in which the executive branch seeks to make court orders optional. This month, the U.S. executive branch blatantly defied a federal judge’s order to temporarily halt the deportation of migrants to El Salvador. The president himself called for the impeachment of the judge who issued the order, along with other judges. In one of the 139 legal cases filed against the Trump administration...