U.S. Attorney General Eric Holder was right to tell the National Urban League last month that despite a Supreme Court ruling in July striking down a key provision of the Voting Rights Act, the Justice Department will still seek to block Texas and other states from changing their voting laws in ways that limit minorities' access to the polls. The short-sighted action by the court's conservative majority threatens to turn back the clock for millions of black and Hispanic voters in states with a past history of discrimination and demands a vigorous response from the Justice Department to protect the right to cast a ballot. Though the court weakened the federal government's ability to act in the interests of democracy, the justices didn't eliminate it, and what Mr. Holder is doing is both appropriate and necessary.

The justices declared unconstitutional Section 4 of the law, which determined which states and counties were required to get federal pre-approval before changing election laws in ways that disproportionately affected minority voters, but erecting barriers to voting based on race or ethnicity is still illegal. Despite the changes the country has experienced since the law was passed in 1965, the laws against voter discrimination still require enforcement, and the Justice Department has the authority to go after states that attempt it.

Mr. Holder is using other provisions of the act to prevent states from enacting changes that were discriminatory in intent, specifically Section 5 of the law, which allows the government to block discriminatory voting laws from taking effect, and Section 3, which permits federal judges to require states and jurisdictions to get Justice Department approval for any changes in voting laws. Although following that process is not as good as pre-clearance — which stopped bad laws before they had a chance to damage minority voting rights — it's better than nothing.

Conservative Republicans immediately branded the attorney general's remarks as an attempt to defy the nation's highest court, or at least do an end run around the justices' intent. It is nothing of the sort. In declaring his intent to go after states that attempt to pass discriminatory voting laws, Mr. Holder is doing exactly what the court said his department can and should do to ensure minority voting rights are protected.

Moreover, if there were any doubt that those rights are in danger, the recent actions of Texas and other states previously covered by the law's "pre-clearance" requirement clearly show why voter discrimination can't be dismissed as a thing of the past. On the same day the Supreme Court issued its ruling, Texas' attorney general announced that a voter-ID law a lower court had blocked as discriminatory in 2011 would go into effect immediately, and over the next week four more former states that had been subject to the pre-clearance requirement — Alabama, Mississippi, Virginia and North Carolina — quickly moved to tighten restrictions on voting.

The disproportionate and discriminatory effect of such laws on minority voters, especially measures imposing photo ID requirements and curbs on early voting, has been well-documented. African-American and Hispanic voters are less likely than whites to have government-issued IDs, and they also make up a larger proportion of early voters. States can't be allowed to use these modern equivalents of the poll tax and literacy tests to re-impose the same old discriminatory practices the law was intended to prevent.

Though clearly much has changed in America over the past 40 years, the federal government still has a vital role to play in defending minority rights. Congress recognized that when it reauthorized the Voting Rights Act nearly unanimously as recently as 2006, and it can still restore the law's full protection by revising Section 4 of the act using more recent data — of which there's no shortage, given the transparent attempts of states like Texas to turn back the clock. Until then, Mr. Holder should spare no effort to ensure that minority voters are able to exercise their most fundamental right in a democracy.