A transgender volleyball player at San Jose State University can continue to compete on the women’s team, a judge ruled Monday, despite complaints from other players who object to the participation of an athlete who is transgender.

The decision by a federal judge in Colorado came two days before a conference tournament involving the team was set to begin. It is the latest chapter in the fierce national debate about whether transgender athletes, particularly transgender women, should be allowed to compete on teams that align with their gender identity.

The controversy has divided the Spartan volleyball team and coaching staff, and drawn attention nationwide.

Eight players for four other colleges in San Jose State’s conference, the Mountain West, had filed a lawsuit seeking to bar the San Jose State volleyball player from competition.

They were joined by women’s volleyball co-captain Brooke Slusser, along with former Spartan volleyball players Alyssa Sugai and Elle Patterson, San Jose State associate head coach Melissa Batie-Smoose and eight players from four schools that have forfeited games against the Spartans. Batie-Smoose was suspended indefinitely after she filed a Title IX complaint against San Jose State University, alleging that Blaire Fleming, the team’s transgender player, conspired with an opponent to help the team lose a match and injure teammate Slusser.

The plaintiffs argued that allowing the player to participate in the tournament would discriminate against women by denying them equal opportunities.

The defendants named in the lawsuit are San Jose State head volleyball Coach Todd Kress, the Mountain West Conference and its commissioner, two administrators at San Jose State, and the board of trustees of the California State University System.

San Jose State has said that it followed all N.C.A.A. eligibility guidelines. Lawyers for the defendants pointed to a Supreme Court ruling in 2020 saying that a ban on sex discrimination in the workplace, part of the Civil Rights Act of 1964, extended to discrimination based on sexual orientation and gender identity.

Judge S. Kato Crews, an appointee of President Biden to the U.S. District Court in Colorado, wrote in his ruling that appellate and Supreme Court precedents had established that the protections of Title IX and the 14th Amendment applied to transgender individuals. Given that, the judge said, the plaintiffs had not shown that they were likely to win their case.

The plaintiffs appealed the judge’s ruling, but a federal appeals court judge today rejected their request for an emergency order.

The judge wrote that the plaintiffs had also weakened their case by not acting sooner. The conference’s transgender participation policy had been in effect since 2022, the judge wrote, and four conference opponents and one nonconference opponent forfeited games against San Jose State beginning in September. He wrote that “the rush to litigate these complex issues now over a mandatory injunction” placed a heavy burden on the defendants “at the eleventh hour.”

His ruling means that the transgender player remains eligible to compete in the tournament, which will feature the six teams in the conference with the best regular season records. They are competing for a spot in the N.C.A.A. Division I tournament in December. San Jose State will play either Boise State or Utah State; each of those teams forfeited earlier games against the Spartans.

San Jose State University wrote in a statement that it “will continue to support its student-athletes and reject discrimination in all forms.”

The San Jose State player has not spoken publicly about how she identifies, and could not be reached for comment. The university has not publicly confirmed whether the volleyball team has a transgender player, citing educational privacy laws. But the defendants did not dispute that a transgender woman was on the team, according to the judge’s ruling.

The player has been a member of the team since the 2022 season. The Mountain West Conference’s records show that the four conference schools that forfeited games against San Jose State this season played the Spartans in previous seasons when the same player was on the team.

The N.C.A.A.’s rules on transgender participation vary by sport, depending on the governing bodies of that sport.

In some sports, like track and field, transgender women are essentially barred from competing in women’s events.

But in volleyball, transgender athletes must submit documentation showing that they have “taken the necessary steps to transition to their adopted gender,” according to guidelines from USA Volleyball, the sport’s governing body.

The N.C.A.A. also says that before transgender women can compete on women’s teams, they must complete one calendar year of testosterone suppression treatment and not exceed certain levels of testosterone, a hormone linked to increased muscle growth and speed, among other physical attributes.

In general, those who favor barring transgender athletes from competing argue that transgender women retain some of the physical advantages they gained when they went through male puberty before they transitioned, giving them an unfair edge in competition with other women. But there is debate about the extent to which testosterone provides a decisive advantage in athletics.

Twenty-five states have laws barring transgender athletes from competing in sports consistent with their gender identity, according to the Movement Advancement Project, an L.G.B.T.Q. advocacy group that tracks legislation. Many of those laws, including those in Idaho and Utah, have been blocked in the courts by legal challenges.

“We’re glad to see this frivolous, hateful and divisive lawsuit be rejected,” Tom Temprano, a spokesman for Equality California, an L.G.B.T.Q. civil rights group, said about the San Jose State case. “This court and many other courts before it have continued to rule in favor of transgender athletes being able to participate in school sports. We hope that courts will continue to do this moving forward.”

In a number of lawsuits filed since 2020, courts have largely upheld the eligibility of transgender women to play on teams that align with their gender identity.

In August, a federal judge in Virginia issued a preliminary injunction stopping Hanover County Public Schools from keeping a transgender middle school student from trying out for a girls’ sports team.

Even so, the court battles appear to be far from over. In March, the N.C.A.A. was sued by several swimmers and athletes from other sports who said the organization had discriminated against women by allowing Lia Thomas, a swimmer who is a transgender woman, to compete for the University of Pennsylvania in the 2022 national championships. The lawsuit is pending.

In 2021, a district judge dismissed a case in Connecticut brought by women assigned female at birth who argued that they were put at a disadvantage by the state’s policy allowing transgender girls to compete in girls’ high school sports. An appeals court disagreed,and the same judge ruled this month that the case could move forward, writing that there was “little guidance” on how courts should interpret policies regarding transgender athletes.

Two other cases, one in Idaho and one in West Virginia, could be taken up by the Supreme Court after federal appeals courts sided with transgender minors.

Rachel Nostrant and Kate Selig are reporters with The New York Times. Reporting was contributed by Amy Harmon, Alain Delaquérière and Seamus Hughes. Copyright 2024, The New York Times.