When Idaho’s governor signed a law last month banning transgender women and girls from competing in school athletic programs for girls, civil rights groups readied themselves for yet another constitutional fight.

The “Fairness in Women’s Sports Act,” or HB 500, requires a student whose eligibility is in dispute to provide a doctor’s note that verifies her “biological sex,” based on one of three things: “the student’s reproductive anatomy, genetic makeup, or normal endogenously produced testosterone levels.” The law, which applies to the state’s public school and higher education systems, is the first of its kind.

“It’s hard to imagine a more invasive thing,” said Nora Huppert, a fellow at Lambda Legal, a national legal organization that fights for LGBTQ civil rights. Two student-athletes are already suing the state.

Idaho’s governor also signed a law prohibiting people from changing the gender markers on their birth certificates to align with their gender identity.

The goal of the legislation targeting trans athletes, experts say, is to codify discriminatory and invasive practices founded on nonscientific reasoning and personal prejudice.

“Sport developed as a masculine pastime—to demonstrate manliness,” and anything that challenges conventional gender norms or behavior threatens societal arrangements and expectations, said Lindsay Pieper, an associate professor of sports management at Virginia’s University of Lynchburg and the author of Sex Testing: Gender Policing in Women’s Sports.

The law goes further than the guidance of the Idaho High School Activities Association, which was already restrictive. Like rules from the International Olympic Committee (IOC) and the National Collegiate Athletic Association (NCAA), it allowed trans girls and women to compete on women’s teams if they had completed one year of hormone therapy. The IOC policy goes further by requiring athletes to demonstrate specific testosterone levels for one year.

“[Testosterone is] the only thing [the IOC is] regulating,” said Kristine Newhall, assistant professor of kinesiology at SUNY Cortland. By zeroing in on testosterone levels, Newhall said, athletic governing bodies have created a measurement for sex only as it pertains to sports that has changed every so often when scientists believe they have a better way to measure sex difference.

“We’ve gone through all these [measures] of sex: genitalia, secondary sex characteristics, chromosomes, and then it’s hormones,” Newhall said, alluding to the relatively recent fixation on testosterone. What this demonstrates is that “science tells us … that there’s no one way to measure sex.”

One of the first public debates about the use of science and “gender verification” to dictate athletic participation was in 1976, when Renée Richards, a trans woman, applied to compete in the U.S. Open and refused to subject herself to the chromosomal test required by the U.S. Tennis Association. Richards won a lawsuit the following year to compete without undergoing the test.

Though we still don’t know what it means to embody a gender, sociocultural forces and athletic governing bodies are attempting to codify “what it means to be a woman,” Pieper said.

“Hard science” that measures chromosomes, genetics, or genitalia is an imperfect measurement of what it means to embody a gender, because scientific discoveries are often influenced by human prejudice, said JayCee Cooper, a 32-year-old amateur powerlifter and trans woman from Minneapolis, Minnesota. “Science exists with a social underpinning. There’s no way to separate that, because we as humans naturally have biases.”

Cooper knows this through her own experience. In late 2018, Cooper was prevented by USA Powerlifting from competing in the women’s category, even though she adhered to the IOC standards of lowered testosterone levels. USA Powerlifting states on its website that trans women have advantages over cisgender women competitors, citing the scientific opinion of a doctor from the organization’s own medical committee. In June 2019, Gender Justice, a nonprofit legal and policy advocacy organization, filed a complaint against USA Powerlifting on behalf of Cooper.

“Advantage isn’t one thing,” Newhall said, and there’s no one bodily reason that an athlete fares better than their competitors. Newhall noted that swimmers with bigger feet might best their fellow athletes on a given day, or that ice skaters with larger lungs might be better equipped for the sport. “Congrats if you have greater lung capacity, then you have greater advantage.”

Even then, many other determinants—including wealth and resources—also dictate ability to compete. The real disadvantage girls and women face in sports have to do with institutions that regulate them, said Sarah Axelson, senior director of advocacy at the Women’s Sports Foundation, an organization dedicated to gender equality in sports.

Axelson called Idaho’s HB 500 a distraction from the real needs of girls’ athletics. According to the Women’s Sports Foundation, 87 percent of NCAA-regulation schools were not in compliance with Title IX standards, which prohibit sex-based discrimination in schools that receive public funding. Girls, both trans and cis, need more opportunities for athletics, not fewer, Axelson said. “Sports have tremendous power for the development of our youth.”

Transgender students are disproportionately more likely than their cisgender peers to feel unsafe at school and be denied basic resources, like use of bathrooms or locker rooms that align with their gender. The new Idaho legislation will make the lives of trans students and anyone who doesn’t conform with conventional gender norms more difficult, Huppert said. “There’s clearly a moral panic around trans people, in particular in the states around trans kids.”

Trans students also experience higher rates of stress and are at higher risk of suicide than their cis peers. HB 500 will exacerbate these issues. “What [Idaho legislators] are saying is, ‘You’re not normal,’” Newhall said.

Anti-trans legislation burdens trans student-athletes with having to assert the legitimacy of their embodied experiences. While Idaho lawmakers argue they are evening out the playing field, they are actually further disempowering trans youth and actively perpetuating anti-trans discrimination.

When trans athletes are able to compete, sports can be empowering and healing. Cooper said when she’s competing, “This is me to a 100 percent degree, and I get to define that for myself. It’s something that nobody can take away. I get out on the platform and I do this thing, pushing myself completely to the limit [and] also pushing other people’s perspectives.”