Tennis legend Martina Navratilova, winner of 18 Grand Slam singles titles, has noted that, when it comes to competitive athletics, “sex segregation is the only way to achieve equality for girls and women.” That is because, on average, males are stronger, faster, and more powerful than females. 

And, yet, with the stroke of a pen, the United States Supreme Court last week called into question the legality of all sex-specific athletic teams.

In Bostock v. Clayton County, the Court ruled that Title VII of the Civil Rights Act of 1964 prohibits workplace discrimination against transgender employees. The statute prohibits discrimination “beacuse of sex”, but it does not mention gender identity or transgender status. 

The majority, in an opinion by Justice Neil Gorsuch, held that the statute refers only to biological sex. But, they reasoned, discrimination on the basis of gender identity is a form of “sex” discrimination because a transgender person’s status can only be defined in relation to his or her biological sex at birth.

Many civil rights activists cheered the holding as a victory for the LGBTQ+ community.  And, indeed, it is. 

But the majority’s reasoning is frighteningly problematic. And it won’t be long before courts extend Bostock to Title IX, the 1972 statute that outlaws sex discrimination in all aspects of education, including athletics. 

Traditionally, courts have interpreted all federal sex-discrimination law as prohibiting policies that favor one sex over the other, not as prohibiting all policies that separate or distinguish between males and females on the basis of biological differences. 

Thus, while Title IX mandates that schools treat male and female athletes equally, no court has interpreted the statute as prohibiting the separation of the sexes for purposes of athletic competition. 

According to a 2016 article by Beth A. Brooke-Marciniak and Donna de Varona in the World Economic Forum, since 1972 there has been “a 545% increase in the percentage of women playing college sports and a 990% increase in the percentages of women playing high school sport.”

None of this progress would have been possible without a binary approach to athletics that takes into account the average differences in athletic performance of males and females. That progress now is in jeopardy.

According to Justice Gorsuch, an employer discriminates “because of sex”any time that an employee’s sex factors into an adverse employment decision.  But just as an employer cannot fire a transgender employee without considering that employee’s biological sex, neither can a school separate the sexes in athletic competition without considering the sex of the participants.  

Suppose, for example, a male student fails to make the men’s college lacrosse team but then tries out for the women’s team and demonstrates that he is a better player than any of the female players. The coach of the women’s team can only deny that player a roster spot if she considers the player’s sex. In this case, the player would be placed on the team but-for his sex. This is exactly what Justice Gorsuch says federal sex discrimination law forbids. 

So what is to stop a male student, armed with the Supreme Court’s ruling in Bostock, from claiming the right to try for a spot (and, potentially, a scholarship) on a women’s team? Absolutely nothing.

When this happens — and it will happen soon —  biological females will lose spots on athletic teams with limited rosters. In head-to-head competitions, female athletes will lose to male-bodied athletes most of the time. This is not equal opportunity. This is male dominance.

Until last week, the debate about male-bodied athletes competing in women’s sports focused almost exclusively on whether male-to-female transgender athletes should be allowed to compete as women.  Today, thanks to Justice Gorsuch, the threat to women’s sports is far greater than most people could have possibly imagined.

In fact, it is quite possible that the Court’s Bostock ruling will pave the way for the elimination sex-segregated sport altogether. 

Indeed, there are activists who seek to do just that. Author Adrienne N. Milner, for example, claims that offering separate male and female athletic teams unfairly stereotypes women as unable to compete with men. Milner argues that sex segregation, like racial segregation, should be prohibited in sport. But, of course, sex and race are not the same.

The effort to eliminate sex-specific athletics may seem like a fringe movement. But the Bostock decision provides activists like Milner with a powerful new weapon. 

As we celebrate the anniversary of Title IX’s passage this week, let’s fight to protect the rights of women and girls to compete on a level playing field.

Jennifer C. Braceras is director of Independent Women’s Law Center