IN THE LATEST battle in the war over voting rights, the Justice Department announced last Thursday its plans to sue Texas over its strict voter identification law, a decision that comes just weeks after Attorney General Eric H. Holder Jr. also promised to challenge the state’s redistricting plan.

States like Texas with particular histories of racial discrimination at the polls had been required to “preclear” proposed changes to voting practices. Federal courts had blocked both of these laws under that preclearance regime last summer, citing the disproportionate impact they would likely have on poor and minority voters. Then the Supreme Court in June invalidated the Voting Rights Act’s Section 5, and Texas wasted no time in charging ahead with both.

As devastating as the Court’s ruling was for the federal government’s ability to protect the franchise, significant portions of the Voting Rights Act still stand. Mr. Holder plans to challenge both of Texas’s proposed laws — and, presumably, others like them that have recently passed in other states — in a circuitous route through the portions of the Act that remain. In his words: “We will not allow the Supreme Court’s recent decision to be interpreted as open season for states to pursue measures that suppress voting rights.”

It’s good to see the Justice Department so emphatically oppose laws that would check minority rights. Unfortunately, fighting them is far easier said than done. Without the preclearance requirement, the Justice Department will have to rely on the Voting Rights Act’s Section 2, which prohibits measures “adopted with the purpose, and will have the result, of denying or abridging the right to vote on account of race, color or membership in a language minority group.”

Section 2, often used to dispute redistricting proposals, may not work against photo identification laws. For one, as recently as 2008, the Supreme Court supported the idea behind voter identification laws, rightly insisting that states do have a credible interest in protecting the legitimacy of elections. Because of that precedent — and without the preclearance calculus in place — it won’t be easy to differentiate between honest identification laws that protect the franchise by offering assistance to those who need it in procuring the required documentation and those laws whose real intent is far less noble. There’s not much question that Texas’s voter identification law is one of the latter, but it’s questionable whether that will be legally compelling under what’s left of the Voting Rights Act.

Ultimately, the ideal solution to this problem is for Congress to update the act. That way, the Justice Department wouldn’t have to fight laws like the one in Texas with piecemeal measures on a case-by-case basis. As the 50th anniversary of Rev. Martin Luther King Jr.’s March on Washington draws near, surely even this Congress can recognize the importance of taking substantive action. The franchise isn’t a partisan issue. As we celebrate the achievements of the civil rights movement, we shouldn’t have to mourn the death of one its most significant and necessary achievements.