“Partisan gerrymandering is nothing new,” writes Chief Justice John Roberts near the beginning of his opinion in Rucho v. Common Cause. “Nor is frustration with it.” The question is what, if anything, federal courts ought to do about it. The answer the chief justice and the four other Republican-appointed justices have endorsed, journalists have been reporting, is nothing.

Actually, judges have a very effective weapon to limit, though not prohibit, partisan districting, which we’ll get to later. But first, let’s be clear that the chief justice is right about the history of the issue. He is correct, first of all, in disagreeing with Justice Elena Kagan’s suggestion in her dissent that partisan districting has gotten much more common and effective in recent years.