NASHVILLE (AP) — A federal appeals court heard arguments on Thursday over a decades-old Tennessee policy that does not allow transgender people to change the sex designation on their birth certificates.

The lawsuit was first filed in federal court in Nashville in 2019 by transgender Tennesseans who say Tennessee's prohibition serves no legitimate government interest while it subjects transgender people to discrimination, harassment and even violence when they have to produce a birth certificate for identification that clashes with their gender identity. They say the policy is unconstitutional.

Last year, a federal judge dismissed the case, ruling that while there are varying definitions of "sex," the term has a very narrow and specific meaning for the purpose of birth certificates in Tennessee: "external genitalia at the time of birth."

Attorney Omar Gonzalez-Pagan, with Lambda Legal, argued the case for the transgender plaintiffs before a three-judge panel of the Sixth U.S. Circuit Court of Appeals on Thursday.

Birth certificates "are not mere records of historical facts or observations," he said. "Birth certificates are critical and foundational identity documents." And in the case of transgender people, those identity documents are incorrect, he argued. He noted that Tennessee does allow changes to birth certificates in cases where the sex is listed as "unknown" at the time of birth.

Proposing a hypothetical, Judge Jeffrey Sutton asked whether it would be constitutional for a state to allow changes to the sex on a driver's license but not a birth certificate since the license could be used for identification instead.

Gonzalez-Pagan said there are cases in which birth certificates are required for identification, like getting a passport.

Sutton also asked if self-identification as transgender should be the only thing needed to change a birth certificate.

"The states are all over the map on how they treat this," he noted. "Some ask for proof of a sex change. Others will ask for proof of treatment, others, just a doctor's note, and others self-designation."

Gonzalez-Pagan did not directly answer at first, but after being pressured by the judge to do so, he said that self-identification is what should be required.

The plaintiffs — four transgender women born in Tennessee — argue in court filings that sex is properly determined not by external genitalia but by gender identity, which they define in their brief as "a person's core internal sense of their own gender." However, they are not asking the appeals court to determine what sex is but rather to send the case back to U.S. District Judge Eli Richardson by ruling that his dismissal of the case without a trial was improper.

Associate Solicitor General Matt Rice, representing the state of Tennessee, argued that Richardson ruled correctly.

"The Constitution does not require states to amend their birth certificates to include a person's gender identity," he said. "Tennessee does not somehow discriminate against transgender persons by merely maintaining a record of a person's sex based off of external genitalia at birth."

Moreover, he said the sex designation is protected government speech. The transgender plaintiffs are not actually arguing that they are treated differently from anyone else, Rice said, "they just want us to convey a different message."

Sutton asked about a separate case in state court where a transgender woman sued the Tennessee Department of Safety and Homeland Security last week after officials refused to change the sex on her driver's license. Tennessee had previously allowed those changes, but the legislature passed a law last year defining "sex" throughout Tennessee code as a person's "immutable biological sex as determined by anatomy and genetics existing at the time of birth."

It made sense, Sutton said, that the birth certificate was a record of the sex at birth while the driver's license was a current identity document.

"It really seemed to lower the stakes, and it also suggested that the state did not have any animus against transgender people," Sutton said.

Rice argued that the legislature's actions in 2023 cannot show that the birth certificate policy, in place for more than half a century, was enacted with animus.

Tennessee is one of five states currently that do not allow transgender citizens to change the sex on their birth certificates, according to data collected by the nonprofit Movement Advancement Project, but many laws and policies regarding identification documents for transgender people are in flux across the United States.

Just this week, transgender, intersex and nonbinary Arkansas residents sued the state over its decision to no longer allow "X" instead of male or female on state-issued driver's licenses or identification cards.