After next year’s census, legislatures in most states will draw new congressional districts, and if one party dominates the legislature, the odds are that the districts will be drawn in a way that will give that party an unfair advantage in the U.S. House. On Thursday, in an appalling act of judicial abdication, a majority of Supreme Court justices said that such a sabotage of democracy is none of their business.

Writing for himself and four conservative colleagues in cases from North Carolina and Maryland, Chief Justice John Roberts essentially threw up his hands when confronted with congressional maps drawn to dilute the voting power of members of the opposing party. The Maryland map was configured by Democrats to eliminate a longtime Republican member of Congress. The North Carolina map was rigged by Republicans to disadvantage Democratic voters.

The parties didn’t even bother to pursue their objectives by stealth. A Republican leader in North Carolina justified partisan mapmaking this way: “I think electing Republicans is better than electing Democrats.” In Maryland, a key figure in the drawing of Democratic-friendly district lines was Rep. Steny Hoyer, the current House majority leader, who referred to himself as a “serial gerrymanderer.”

But partisan gerrymanders have a corrosive effect on democracy, enabling those in power to entrench themselves for long periods of time and in excess of their electoral support – so that voters are, in effect, participating in elections rigged to result in a particular outcome. Lower federal courts had no trouble deciding that the gerrymandered maps deprived some voters of their constitutional rights. But Roberts professed doubt that he and his learned colleagues were capable of bringing similar judgment to bear

in a consistent way. Therefore, he concluded, allegations of unconstitutional partisan gerrymandering are “nonjusticiable” – that is, they are incapable of being decided by a court.

In a 2004 case, then-Justice Anthony Kennedy floated a legal test for evaluating partisan gerrymandering based on the First Amendment. It said that maps deliberately drawn to unfairly advantage the majority party in the legislature create an unconstitutional burden on citizens “because of their participation in the electoral process, their voting history, their association with a political party, or their expression of political views.” That makes sense, and lower courts in the Maryland and North Carolina cases concluded that the plaintiffs’ First Amendment rights were violated.

But Roberts said the Supreme Court couldn’t judge whether a gerrymander was unfair because there are many definitions of “fairness” and choosing among them “poses basic questions that are political, not legal.”

Actually, it’s not that hard to determine whether a map has been manipulated for partisan gain. Roberts himself conceded in his opinion that the Maryland and North Carolina redistricting plans were “highly partisan, by any measure.” Moreover, contrary to Roberts’ implication, it’s possible to correct highly partisan maps without embracing the idea that parties have to be represented in Congress in proportion to their statewide support.

Despite Roberts’ suggestion that redistricting cases are too political for judges to decide, lower courts have been dealing with these questions for some time. And, as Justice Elena Kagan pointed out in a powerful dissent, workable standards for courts to apply have emerged. A gerrymander is unconstitutional if it is intended to entrench a particular party in power; if it accomplishes that objective by diluting the votes of citizens who favor the other party; and if, when these factors exist, the state can’t point to a “legitimate, nonpartisan justification” for the map.

In denying victims of partisan gerrymandering their day in court, Roberts assured them that there are other avenues to reform. He noted that some states have placed the power to draw new districts with independent commissions and that state supreme courts have struck down gerrymandered maps on the basis of their own state constitutions.

And yet, according to the majority, the evils of partisan gerrymandering can’t be addressed by the highest court in the land despite the danger it poses to political equality and electoral fairness. As Kagan put it: “For the first time ever, this Court refuses to remedy a constitutional violation because it thinks the task beyond judicial capabilities.”

To borrow a phrase from the late Justice William Brennan, the majority’s claim that courts can’t address this problem is “arrogance cloaked as humility.”