The U.S. Supreme Court will hear oral arguments this week on whether states can keep Donald Trump from appearing on primary election ballots for president based on the U.S. Constitution’s insurrection clause. More seriously, it could decide that Trump is ineligible to be president again even if he wins the November election. We should hope for two outcomes: First, that the court does not use technicalities and procedural issues to evade a clear decision; and second, that it allows common sense and the fate of democracy to loom large in its decision. The case before the court is an appeal...