A federal court in Washington ruled on Thursday that a Texas Voter ID law violates the Voting Rights Act, effectively blocking the law from taking effect.

The unanimous three judge district court ruled, "The State of Texas enacted a voter ID law that - at least to our knowledge - is the most stringent in the country. That law will almost certainly have retrogressive effect: it imposes strict, unforgiving burdens on the poor, and racial minorities in Texas are disproportionately likely to live in poverty."

In the weeks leading up to the election, the law - passed by a Republican-led Texas legislature - has gained particular attention as supporters said it was meant to protect voter integrity, while critics claimed it would lead to voter suppression. The Voter ID law requires people voting in person to provide certain government-issued photo IDs when the come to the polls.

Texas Attorney General Greg Abbott released a statement today vowing to appeal the decision. "The Supreme Court of the United States has already upheld Voter ID laws as a constitutional method of ensuring integrity at the ballot box. Today's decision is wrong on the law and improperly prevents Texas from implementing the same type of ballot integrity safeguards that are employed by Georgia and Indiana - and were upheld by the Supreme Court. The State will appeal this decision to the U.S. Supreme Court, where we are confident we will prevail."

The law was passed in 2011, but was subject to approval by federal officials as required by the Voting Rights Act (VRA). Section 5 of the VRA requires certain jurisdictions with a history of voter discrimination to "pre-clear" any changes to voting laws with the Department of Justice or a federal Court in Washington. Covered jurisdictions include 9 states and parts of 7 additional states.

Judge David Tatel, in writing the opinion, said today that under Section 5 the burden was on Texas to show that the law would not be harmful. Tatel said, "Uncontested record evidence conclusively shows that the implicit costs of obtaining [qualifying ID] will fall most heavily on the poor and that a disproportionately high percentage of African Americans and Hispanics in Texas live in poverty."

The case has been of interest to election law experts because not only is Abbott defending his state's voter ID law, but Texas is also challenging the constitutionality of Section 5.

"The Texas case is important because it focuses attention on the potentially racial disparate impact of the laws, and it also highlights how some rules apply to some states and not to others," said Nathaniel Persily of Columbia Law School.

In court papers, Texas argued that the voter ID law was designed to help detect illegal conduct at the polling place, deter those who attempt to illegally interfere with the democratic process, and prevent election fraud in the future.

"Requiring a photo ID to vote does not impose a legally significant burden because proving one's identity with a photo ID is a routine feature of modern life," Abbott wrote.

But the Department of Justice said that instances of in-person voter impersonation are "exceedingly rare" and that while current Texas law permits 8 categories of photo and non-photo ID, the new law permits only 4 narrower categories of photo ID.

"On a background of growing Hispanic population and voting strength, and a history of racial discrimination not abandoned until federal intervention, the Texas Legislature used deviations from ordinary legislative procedure to pass a voter identification law whose restrictions exceed those imposed by any other states," wrote Assistant Attorney General Thomas E. Perez of the Department of Justice.

Perez said that the "state of Texas has failed to carry its burden under Section 5 to prove that the [law ] neither has the purpose nor will have the effect of denying or abridging the right to vote on account of race, color or membership in a language minority group."

This week in Washington another panel of federal judges is hearing a separate challenge to South Carolina's voter ID law. It was passed in May 2011 and signed into law by Republican Gov. Nikki Haley. Like Texas, South Carolina is a covered jurisdiction under the Voting Rights Act and the law must be pre-approved. The law requires South Carolinians who vote in person to present one of five forms of photo ID. If the voter is unable to present an acceptable form of identification, the act includes a provisional ballot procedure. The ballot will be counted so long as the voter brings the ID to the county board of registration and elections before certification. If the voter lacks a photo ID due to a "reasonable impediment," he may execute a simple affidavit and cast a provisional ballot.

Critics of the South Carolina law argue that a "reasonable impediment" is not clearly defined.

Wendy Weiser of the Brennan Center for Justice, who opposes both the Texas and South Carolina laws, said the bottom line is some Americans won't be able to vote.

"The problem with these new laws is not that they ask people for ID, but that they are inflexible and require people to show a small number of ID's that 21 million Americans don't have. The most common of these ID's is a driver's license, which many older Americans and people of color who do not drive don't have. This country was founded on the principle that we are all created equal and it is wrong to pass laws that deny some Americans the equal opportunity to vote. "

Paul D. Clement, who is representing South Carolina, argues in briefs, "The overwhelming majority of American voters support photo ID requirements as a common sense means of ensuring that those who show up to vote are eligible to do so, (and have not already voted)."

South Carolina argues indirectly that it should no longer be subject to Section 5. Texas makes the case directly arguing in part that other states have been able to enact similar Voter ID laws.

According to Jennie Bowser of the National Conference of State Legislatures, there are a total of 33 states with some kind of voter ID law.

"Most of them," Bowser said, "are not as controversial as the kind of voter ID laws we are talking about in Texas and South Carolina because either they allow a wider range of IDS that in many cases don't have to bear a photo, or because they are not as strict. There is a mechanism for voters without ID to cast a ballot that will be counted."

"There are two main differences between the old laws and the new laws in Texas and South Carolina. First, under the old law, there was a form of ID that didn't bear a photo that was acceptable for voting purposes. Under the new laws you have to have a photo ID to vote. Second, under the new laws, if a voter doesn't bring a photo ID to the polls on election day, the ballot will not be counted unless the voter returns to election officials within a few days to show an ID. Under the old laws you didn't have to do that to get your ballot counted. "

Judge Tatel emphasized that today's ruling applied only to Texas' voter ID law. "Nothing in this opinion remotely suggests that section 5 bars all covered jurisdictions from implementing photo ID laws. To the contrary, under our reasoning today, such laws might well be pre-cleared if they ensure (1) that all prospective voters can easily obtain free photo ID, and (2) that any underlying documents required to obtain that ID are truly free of charge." He mentioned the fact that the Department of Justice had pre-approved a voting ID law in Georgia which requires each county to provide free election ID's and allows voters to present a wide range of documents to obtain the IDs.