Colorado has some of the most liberal laws in the nation to protect the rights of transgender people, but it has not come anywhere close to solving the controversy of trans people playing sports. 

When the Colorado State University women’s volleyball team won the conference championship last month, defeating a team with a transgender player, it raised renewed questions about a simmering issue. 

The title game came after some other teams, including Wyoming, Utah State and Boise State, forfeited their matches against San Jose State, refusing to play a team with a transgender woman on the roster. And it came as a new wave of trans people are trying to move to Colorado because of anti-trans rhetoric during the presidential campaign, a flood of state-level proposals against transgender rights, and a looming U.S. Supreme Court decision on a Tennessee ban of gender-affirming medical treatment for adolescents.

Colorado for years has been considered a safe harbor for transgender people. It has one of the simplest processes in the nation to change the gender marker on a birth certificate — some states require proof of surgery or prohibit changing the gender marker at all. The Colorado Anti-Discrimination Act prohibits discrimination in housing and employment based on gender identity, and the state has disallowed discrimination in private health insurance plans based on gender identity.

Last year, Colorado became the first state in the country to explicitly include gender-affirming medical care in its insurance requirements, meaning that insurance companies must cover the care in individual plans and small group plans. Gender-affirming care for adolescents, which can include hormone therapy and puberty blockers, has been banned in 26 states. Colorado, though, passed a shield law in 2023, protecting the right to gender-affirming care, including for kids and teens. 

Despite Colorado’s status as a trans-friendly state, barriers remain, especially surrounding the sticky topic of competitive sports. We checked in with some experts on the laws and science surrounding the controversy. 

Do trans athletes have to disclose their sex at birth?

In Colorado, Jude’s Law allows trans and nonbinary people of any age to change their birth certificate. People can switch the gender marker on their official document to F or M, or even X, and the birth certificate does not note that it was amended. No doctor’s note is required, and people are not required to have had gender-reassigning surgery to switch the gender marker. 

Does that mean trans people could play a high school or college sport without disclosing the gender on their original birth certificate? No, not under current law. 

The Colorado High School Activities Association, the governing body for high school sports in the state, requires that trans students disclose that they are trans to their school so that the school can “perform a confidential evaluation to determine the gender assignment” for the athlete. The student and their parents must notify the school in writing that the student’s gender identity differs from the one they were assigned at birth.

Transgender athletes have a right to play — but the school’s evaluation determines whether they can play with the team that matches their gender identity.

The school can ask for — but not require — health records verifying the student’s gender identity or hormone therapy. The Colorado High School Activities Association can review the school’s athletic eligibility decision, and families can appeal to the state association.

“Even when there may be policies that seem theoretically permissive, the bureaucratic and practical barriers of making the policy truly acceptable to trans people are large,” said Scott Skinner-Thompson, a law professor at the University of Colorado. While Colorado is considered pro-trans, “in practice, there are tons of barriers.”

In 23 states, trans women and girls are banned from competing in women’s sports, according to Skinner-Thompson’s research. In Florida, this ban includes all competitive, intramural or club teams in middle school, high school and college. 

The National Collegiate Athletic Association policy says that transgender athlete participation is determined by the national governing body of that sport. The recent women’s volleyball controversy is proof the issue is far from sorted out. 

Two days before the tournament, a federal judge in Colorado ruled that the trans woman San Jose State player could continue to compete on the women’s team. Players for other colleges in the Mountain West Conference, and even the co-captain of the San Jose State team and a former assistant coach, argued in the lawsuit that allowing the trans woman to play was discrimination against women.

The San Jose State player, who played girls volleyball in high school, was outed as transgender in on the website Reduxx in April, before her third season on the team. Teams that had played San Jose State in prior years forfeited games, though they did not say why. Boise State was the first to forfeit, followed by Wyoming, Utah State and Nevada. The governors of all four states said they supported the team decisions and fairness in women’s sports.

Half of states now have laws restricting transgender athletes from playing sports consistent with their gender identity. Although the bans also affect transgender men in male sports, the crux of the debate has centered on transgender people who transitioned to female. 

Is it “fair” for trans women to play against women?

Dr. Bradley Anawalt, an endocrinologist and professor at the University of Washington School of Medicine, hates this question a lot. Because so much in sports isn’t “fair.”

Consider the Ivy League collegiate swimmer Lia Thomas, who competed for the University of Pennsylvania men’s team for three seasons, then transitioned and joined the women’s team. In 2022, she was the first transgender athlete to win an NCAA Division I national championship. 

Anawalt recalled a statement from a cisgender woman swimmer who wished Thomas well, but pointed out that she missed qualifying for regionals by one position. 

“So what’s fair?” he asked. “That’s the sticky part of this. We are going to have to wrestle with this.” 

Is it unfair that people who are 7 feet tall are more likely to excel at basketball? “You don’t even have to be any good,” Anawalt said. “You just have to be tall.” 

Or consider the story of Finnish cross-country skier Eero Mäntyranta who dominated the sport and competed in four Olympics in the 1960s and 1970s. He wasn’t transgender, but he had a genetic condition that allowed his body to produce more red blood cells than average humans, and therefore, had better endurance. 

“Should we have drained his blood before he competed?” Anawalt asked.

In 2016, Colorado Springs transgender cyclist Jillian Bearden edged out the competition at the El Tour de Tucson, finishing in just over four and a half hours. While the second-place finisher declined the comment, the woman who came in third, Suzanne Sonye, had an interesting answer about whether she thought it was fair that Bearden was allowed to compete. 

“I’ll take her on any day, but that’s just me. I’ll take on men, too,” she said, according to Outside Magazine’s Velo. “Regardless of testosterone levels, she’s got muscle memory and a lung capacity that I could never build up. I could never match a pro man. How fair is that to her female competitors?”

What does the research say about gender advantage?

Men on average are stronger and faster than women. They’re also taller on average, and have larger hands. But the data on how much this matters in sports, especially when taking into account testosterone blockers, is incomplete. 

Scientific studies about gender identity and sports are limited. Some of the best data comes from the military. 

In a study of 46 trans women in the U.S. Air Force, the differences in strength and speed between trans women and cis women decreased significantly in the two years after the trans women transitioned. In the first two years after transitioning from male to female, trans women could do 10% more pushups and 6% more situps than their cisgender women peers. After two years of hormone therapy, the number of pushups and situps was about equal. 

The advantage transwomen had in the speed at which they could run 1.5 miles decreased as hormone therapy continued, but trans women were still 12% faster than cis women more than two years out.

“Those studies show that within one to three years, many differences between a cis woman and a transwoman will disappear,” Anawalt said.

And yet, he said, “in an elite athlete, the difference between winning a gold medal in the 100 meters in both men and women’s is often a hundredth of a second — 12% is a lot of time.”

For elite athletes, there’s not much data. “We have examples. Case reports. Not science,” Anawalt said. 

One “case report” centers on professional transgender tennis player Renee Richards, who first competed as Richard Raskin and is considered the first known trans woman to play a professional sport.

In men’s tennis, Richards was among the county’s top college players while at Yale and competed in the U.S. Open five times. After going through gender-reassignment surgery and competing in women’s tennis, Richards, at 6-foot-2, played in the 1977 U.S. Open and reached the doubles final. 

How much does puberty matter?

For girls and boys under age 10, there is no difference in physical strength or speed, Anawalt said. It’s puberty, and the increase in testosterone for boys — around age 11 for girls and age 11-13 for boys — that changes this. 

Children who receive puberty blockers as part of the gender-affirming medical care typically receive the treatment soon after puberty begins, and so far, there is little evidence to show this affects their size. 

Research has found that children who were assigned male at birth but identify as female will grow to within about an inch of the height they would have been without hormone blockers. Hormone treatment before puberty ends likely doesn’t affect the size of their hands and feet too much, though there isn’t great data on this, Anawalt said. 

Height, larger hands and larger feet are advantages for some sports, including volleyball and basketball, but perhaps don’t matter in others. 

Science, no matter how many studies, isn’t likely to settle the debate, Anawalt said. 

“This is a social justice question,” he said. “Everyone is qualified to answer that question.”

It’s interesting, said Skinner-Thompson at CU, that the country is so focused on transgender people playing sports. 

“It’s not to say that sports aren’t important,” he said. “But taking a step back, the things that trans people need are the same things that everybody needs. Economic security. Homes. Jobs. Not to be incarcerated. To be able to go to school. To be able to participate in society. Trans people just want the space to live.”