Texas’ voter ID law faces a fresh round of legal scrutiny in New Orleans on Tuesday, the next step in a long-winding case that may be headed for the U.S. Supreme Court.

Three judges on the U.S. 5th Circuit Court of Appeals will hear arguments from Texas Solicitor General Scott Keller and lawyers for the plaintiffs, including minority groups and the U.S. Department of Justice. The case asks whether Texas intentionally discriminated against Hispanics and African-Americans when it passed what are widely considered the nation’s strictest rules for the identification voters must present at the polls.

The dispute stands out in the national debate over recently tightened identification requirements in many Republican-controlled states, and could factor into whether Texas might – once again – need federal approval to enact new election laws.

The Texas law requires most citizens (some, like people with disabilities, can be exempt) to show one of a handful of allowable photo identifications before their votes can be counted. Acceptable forms include a state driver's license or ID card that is not more than 60 days expired at the time of voting, a concealed handgun license, a U.S. passport, a military ID card or a U.S citizenship certificate with a photo. The acceptable list is shorter than any other state’s.

Experts say more than 600,000 Texans lack such identification. Those citizens can obtain “election identification certificates” free of charge, but must present a copy of their birth certificate. Searching for and obtaining copies of birth certificates can cost between $2 and $47 – charges critics say amount to a “poll tax.”

The state argues that the law bolsters ballot security and prevents election fraud. Attorneys for the state say there is no evidence the law will keep legitimate voters from casting ballots.

“Safeguarding the integrity of our elections process is a top priority of General Ken Paxton’s administration and is essential to preserving our democracy through preventing voter fraud and promoting voter confidence,” Cynthia Meyer, a spokeswoman for the state’s attorney general, said in an email.

Opponents claim the Texas law violates the federal Voting Rights Act and is an attempt to cut into the electoral strength of the state’s growing minority population — people less likely to have photo identification or the means to obtain a certificate for the election.

“It’s evident that the Texas Voter ID law discriminates against minority voters in Texas, a fact already proven in court," U.S. Rep. Marc Veasey of Fort Worth, a plaintiff in the case, said in an emailed statement. “While it is never wise to predict the outcome of a court decision, I believe the evidence is overwhelming and I’m hopeful that this law will ultimately be struck down."

Gov. Rick Perry signed the law in 2011, kick-starting its convoluted journey through the federal court system.

The rules were on hold until 2013, when the U.S. Supreme Court struck down part of the Voting Rights Act, ruling that Texas and other states with a history of racial discrimination no longer automatically needed federal preclearance when changing election laws.

Last October, U.S. District Judge Nelva Gonzales Ramos of Corpus Christi ruled that the Texas ID law “constitutes an unconstitutional poll tax” and “has an impermissible discriminatory effect against Hispanics and African-Americans, and was imposed with an unconstitutional discriminatory purpose.”

That ruling came just one month before Election Day, and the U.S. Supreme Court allowed the state to enforce the law during the 2014 general election. Some Democrats blamed the law for Texas’ particularly low voter turnout.

In her 147-page ruling, Ramos said there were no “smoking guns” proving Texas lawmakers intentionally discriminated when passing the law – such as making anti-African-American or anti-Hispanic statements – but she said wide-ranging evidence proved the state’s intent to discriminate.

That included a lack of “any accommodations for indigents, who the legislature knew were disproportionately African-American and Latino,” and a “racially charged” legislative session that saw several proposals that “exhibited an anti-Hispanic sentiment — anti-immigration laws, an effort to abolish sanctuary cities — and there were even concerns about leprosy being raised.”

In its brief, Texas called the ruling “manifestly erroneous” and based upon “weak and inconclusive circumstantial evidence."

Daniel Tokaji, an elections expert at Ohio State University's Moritz College of Law, called the plaintiffs’ findings of fact “very informed and thorough,” and more than they needed to argue that the law violates the Voting Rights Act.

“It’s what sets the evidence in Texas apart from all the other states,” he said. “There’s just much stronger evidence of intentional discrimination against racial minorities here.”

Rick Hasen, a professor at the University of California, Irvine School of Law, called the dispute a “test case” for the Department of Justice, following the 2013 decision that struck down the formula used to determine when a state election law needs federal review, but gave Congress the option to develop new criteria.

“The Department of Justice is seeking in this case not only to get Texas’ voter ID law struck down, but also to get Texas covered again under the preclearance provision of the Voting Rights Act,” Hasen said.

The 5th Circuit is considered among the most conservative in the nation, but Democrats appointed two of the three judges set to hear Tuesday’s arguments. President Bill Clinton appointed Chief Judge Carl Stewart, and Judge Nannette Brown is an Obama appointee. President George W. Bush appointed Judge Catharina Haynes.