HOUSTON — (CNN) An appeals court ruled late Wednesday that a key portion of Texas’ tough voter ID law violates Civil Rights Act protections barring discrimination against black and Hispanic voters.

A panel for the Fifth Circuit Court of Appeals determined the Texas law violated Section 2 of the 1965 Voting Rights Act, but did not go so far — as plaintiffs had argued — that it amounted to a poll tax.

The state could seek a full review by the entire court. The victory could end up being short-lived, UCLA Law Professor Rick Hasen wrote in an analysis.

“As I noted when this panel was drawn, this is about the most liberal panel plaintiffs could have expected in the 5th Circuit,” wrote Hasen, who specializes in election law. “This also strikes me as an opinion written as narrowly as possible to still give a victory to the plaintiffs.”

The voter ID law, one of many throughout the nation at the center of an ongoing political battle, requires voters to show a valid government identification before voting.

Supporters of the laws, mostly Republicans, say it protects against voter fraud. Texas’ law is just one of many enacted in Republican-dominated states in recent years.

But groups challenging the laws, including the Justice Department, have argued that the measures effectively keep poor residents and minorities out of voting booths because they often lack government IDs or the ability to get a valid ID.

“More than half a million registered voters do not have the kind of ID required by Texas’s harsh new law. Texas should heed the admonishment of three courts, abandon their discriminatory law, and start working to make sure Texas voters can make their voices heard,” Myrna Perez, deputy director of the Brennan Center for Justice at New York University, said in a statement.

The fight over voter ID laws is considered to be the most important electoral legal battle since the Supreme Court struck down federal oversight of voting in nine states, a powerful tool that was central to the 1965 Voting Rights Act.

The-CNN-Wire ™ & © 2015 Cable News Network, Inc., a Time Warner Company. All rights reserved. (Photo: CNN)