The case centers on Lindsay Hecox, a student at Boise State University who, according to counsel's representations at the preliminary injunction stage, suppressed her testosterone for over a year and took estrogen, then sought to compete on women's teams under Idaho's H.B. 500 — the Fairness in Women's Sports Act — which categorically excludes all students with a biological sex of male from women's teams. The Ninth Circuit upheld a preliminary injunction against the law. Idaho Governor Bradley Little and the state petitioned the Supreme Court, with the federal government appearing as amicus supporting the petitioners.
The argument's most contested exchanges turned not on the underlying science but on a foundational equal protection question that Justice Kagan described as surprisingly sparse in the case law: whether an as-applied equal protection challenge to a facially valid sex-based classification can exist at all. Alan Hurst, Idaho's Solicitor General, argued that equal protection doctrine asks whether a classification is valid, not whether it makes sense in individual situations, and that forcing the state to justify a law as applied to each plaintiff would effectively convert intermediate scrutiny into strict scrutiny. Hurst acknowledged that his position means an as-applied argument of this kind is simply not available.
Hashim Mooppan, the Principal Deputy Solicitor General arguing for the United States as amicus, offered a partial concession — he allowed that a sufficiently large subgroup, perhaps a third of the relevant population, might theoretically bring such a claim — but argued that a fraction of a percent of men, the group at issue here, is far too small. He pointed to Michael M. and Nguyen as cases where the Court declined to carve out individuals for whom the law's justification did not apply. Justice Jackson pressed back, arguing that the Court has consistently said facial challenges are hard to win and as-applied challenges are the preferred mode of adjudication, and questioned why a person who can demonstrate the law operates unconstitutionally as to them should be denied any remedy.
Kathleen Hartnett, arguing for Hecox, contended that on the preliminary record, circulating testosterone after puberty is the main determinant of sex-based biological advantage that H.B. 500 sought to address, and that Hecox had mitigated that advantage. She argued that Caban and Lehr, read together, support the availability of as-applied equal protection challenges for a discrete subgroup where the state's rationale does not apply. She distinguished the untalented cisgender boy hypothetical — which several justices raised — by noting that such a person would still carry the same circulating testosterone advantage and thus would not be similarly situated to female athletes.
Mootness occupied substantial argument time. Hecox filed an affidavit with the Court stating she has permanently stopped playing sports covered by the ban and will not try out for any school-sponsored women's sports. Hurst argued the case is not moot, pointing to the district court's order striking a notice of dismissal and Hurst's representation that the district court concluded Hecox's plans had changed before and could change again, and that the maneuver was somewhat manipulative in order to escape the Supreme Court's jurisdiction. Justice Sotomayor compared the situation to Acheson Hotels, where the Court directed a case be considered moot after the plaintiff voluntarily dismissed with prejudice, and noted that a Munsingwear GVR has been agreed to, meaning the Court's analysis in this case will inform any new Ninth Circuit decision. Hurst countered that, unlike in Acheson Hotels, no one disputed the plaintiff's plans in that case, whereas here the district court did not credit Hecox's stated plans.
Justice Gorsuch asked both sides about whether transgender status should be recognized as a discrete and insular class warranting heightened scrutiny in its own right, given a history of de jure discrimination. Hartnett argued that transgender people were categorically excluded from immigration to this country under an umbrella of being classified as psychopaths — pointing to the Boutilier decision and congressional reports from 1952 — and that cross-dressing statutes in major cities subjected transgender people to criminal penalties for leaving their homes. Hurst argued the history does not compare to that of race or sex classifications, citing Justice Alito's concurrence in Skrmetti. In rebuttal, Hurst argued that if there is no transgender status classification under Skrmetti, there certainly cannot be one here, and urged the Court to resolve the case on rational basis review.