“History,” wrote Chief Justice John Roberts in surely one of the most irrefutable sentences ever to appear in a U.S. Supreme Court decision, “did not end in 1965.” To which Justice Ruth Bader Ginsburg, citing Shakespeare and Santayana, replied: True, but it didn’t start then, either.

This dispute over how and when to measure history is at the heart of the court’s 5-to-4 decision striking down a crucial provision of the Voting Rights Act of 1965, a law whose historic accomplishments have been lauded by Roberts himself. His 24-page opinion and Ginsburg’s 37-page dissent amount to an argument over whether it’s time for the U.S., and in particular the American South, to move on.

Roberts’ version of history got more votes. That doesn’t mean it’s correct, but it does mean an end to a chapter in America’s decades-long effort to give meaning to the 15th Amendment’s guarantee of the right to vote regardless “of race, color, or previous condition of servitude.” That effort will and must continue, and it’s up to Congress to show the way.

Before we get to how, let’s dwell on a little history. The Voting Rights Act outlaws discriminatory voting practices nationwide. But it pays special attention to the South, because Congress was worried about the region’s long history of disenfranchisement. In all or parts of 15 states, mostly in the South, local officials were required to get federal approval before making any changes to election rules. Which jurisdictions needed to ask for permission, called “preclearance” in legal terms, was defined in the law.

These rules regarding who needs preclearance were pronounced unconstitutional today. The formula Congress used to single out districts used data about voters and elections from the 1960s and 1970s. “Our country has changed,” Roberts wrote, “and while any racial discrimination in voting is too much, Congress must ensure that the legislation it passes to remedy that problem speaks to current conditions.”

Ginsburg’s dissent, notable for its length and astringency, amounts to a plea for judicial restraint, especially when it comes to voting-rights legislation. “When confronting the most constitutionally invidious form of discrimination, and the most fundamental right in our democratic system,” she wrote, “Congress’ power to act is at its height.”

At least Roberts and Ginsburg agree on this much: Congress has to do something. “Congress may draft another formula,” Roberts wrote, in one of his more disingenuous sentences. Congress can’t agree even to let the post office stop Saturday mail delivery.

One of the beauties of the judicial branch, of course, is that it can pretend to be above politics: Whether the legislative branch is capable of acting is separate from whether it is permitted to. In the case of voting rights, Congress has an obligation to act.

There’s at least a chance it’s not impossible. After all, Congress passed the existing Voting Rights Act five times; the most recent vote was almost unanimous. And Section 2, which prohibits voter discrimination nationwide, is as valid today as it was yesterday, or 48 years ago. The difference is that now the burden of proof is on voters to show discrimination, not on jurisdictions to show there isn’t any.

One way to update the law may be to make it more universal. Blatantly discriminatory practices such as literacy tests are no longer in use. But other requirements, such as strict voter ID laws or restrictions on early voting, also have a disproportionate impact on minority voters. Legislation focusing on the right to vote more broadly would have a better chance of passage than any bill attempting to single out jurisdictions for special treatment.

The great value of the preclearance provision the court invalidated today was that it kept discrimination from happening; the Justice Department used it to prevent a Texas voter ID law from taking effect last year. (That requirement, says the state’s attorney general, is now law.) Congress’s hardest task, working with state and federal officials, will be to come up with an equally effective strategy.

It’s not surprising that Roberts and Ginsburg focused on the history of voting rights in the U.S., or that they disagreed. Members of Congress will surely disagree, too. They don’t have the luxury, however, of arguing about the past. The future of voting rights is now in their hands.

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