This story was updated at 2 p.m. Friday to include statements from Houston Mayor Sylvester Turner and Texas Values President Jonathan Saenz.

AUSTIN — The Texas Supreme Court said Friday that while same-sex marriage is legal, the "reach and ramifications" of the rights of gay couples have yet to be determined.

In a unanimous decision, the nine-member court reversed a lower court's ruling favoring the city of Houston's decision to extend health and life insurance benefits to the spouses of city employees in same-sex marriages. The court ordered the case sent back to the trial court in Houston.

The decision keeps alive the fight over same-sex unions in Texas just days after LGBT Americans celebrated the anniversary of the landmark ruling that handed them the right to marry.

In its ruling Friday, the Texas high court acknowledged that the U.S. Supreme Court legalized gay marriage nationwide two years ago in Obergefell vs. Hodges, but added that it is unclear what other rights the decision extends to same-sex couples. That must be hashed out in the courts in cases like this one, it said.

What happens next is largely up to Houston. City officials could appeal the decision directly to the U.S. Supreme Court or could choose to head back to trial. They did not comment Friday on what path the city would take, saying they are considering their legal options.

"The City of Houston will continue to be an inclusive city that respects the legal marriages of all employees," Mayor Sylvester Turner said. "Marriage equality is the law of the land, and everyone is entitled to the full benefits of marriage, regardless of the gender of their spouse."

On a practical level, the decision doesn't have an immediate effect on LGBT city employees in Houston. Their spouses will continue to receive benefits, as they have for years, while the case continues to be litigated.

The case dates to 2013, when two local taxpayers sued then-Houston Mayor Annise Parker, the city's first openly gay mayor. Relying on a legal opinion from the city attorney, Parker had decided to extend spousal benefits to gay couples, even though an amendment to the city charter banned the practice.

In their lawsuit, Jack Pidgeon, a pastor, and Larry Hicks, an accountant, argued no city employee has a "fundamental right" to receive government-subsidized spousal benefits and that it was "perfectly constitutional" to extend benefits to some married couples and deny them to others.

When Obergefell was decided 18 months later, the state of Texas and government-funded entities, like universities, began extending spousal benefits to same-sex couples in their employ. But Pidgeon and Hicks continued to fight the city's benefits policy.

The Texas Supreme Court initially refused to take up the Houston case after Obergefell. But after pressure from the top elected Republicans in the state, including Attorney General Ken Paxton, Gov. Greg Abbott and Lt. Gov. Dan Patrick, the high court made the unusual decision to reopen the case.

On Friday, the justices said the Obergefell ruling did not detail what additional rights, other than marriage, are guaranteed to same-sex couples.

"Pidgeon and the Mayor, like many other litigants throughout the country, must now assist the courts in fully exploring Obergefell's reach and ramifications, and are entitled to the opportunity to do so," Justice Jeffrey Boyd wrote in the court's decision. "We reverse the court of appeals' judgment, vacate the trial court's temporary injunction order."

Conservative groups hailed the ruling as protecting traditional marriage, while those fighting for the rights of lesbian, gay, bisexual and transgender Americans called it an attempt to "undercut" the rights of the LGBT community.

"The Texas Supreme Court's decision this morning is a warning shot to all LGBTQ Americans that the war on marriage equality is ever-evolving," said Sarah Kate Ellis, president of national LGBT rights group GLAAD. "Anti-LGBTQ activists will do anything possible to discriminate against our families."

Jonathan Saenz, president of Texas Values, the organization representing Pidgeon and Hicks, called the ruling "a huge win for Houston taxpayers."

"It's clear that the payment of same-sex benefits by the city of Houston is still illegal under state law. We look forward to continuing our litigation in the trial court," Saenz added.

Dale Carpenter, a constitutional law professor at Southern Methodist University, disagreed with the justices' decision. A more proper ruling, he said, would have directed the trial court to uphold Houston's benefits program in light of the 2015 Supreme Court case.

Sooner or later, the case will likely end up before the U.S. Supreme Court, he added: "They treat Obergefell like it's just about a marriage license and abstract recognition when it's so much more than that."