The Supreme Court on June 30 upheld West Virginia and Idaho laws prohibiting boys in girls’ sports.

The court, in a 6–3 ruling, held that the laws did not violate Title IX, which bars sex discrimination in education, or the equal protection clause of the 14th Amendment.

“Title IX allows schools to provide separate women’s and men’s sports teams defined by biological sex, and West Virginia has permissibly maintained female sports for biological females consistent with Title IX,” Justice Brett Kavanaugh wrote in the majority opinion.

The court’s ruling clarifies that when Title IX refers to sex, it “cannot plausibly be interpreted to refer to anything other than biological sex.”

Justices Sonia Sotomayor, Ketanji Brown Jackson, and Elena Kagan dissented. The three liberal justices agreed with the majority’s decision to rule in favor of West Virginia on Title IX but suggested the majority acted too quickly in how it handled the equal protection arguments.

The decision is expected to ripple through other states by providing legal guidance for legislatures that address the issue.

The cases, known as West Virginia v. B.P.J. and Little v. Hecox, arose out of a federal appeals court ruling holding that the state’s law violated the 14th Amendment. More specifically, they said that the law violated the equal protection clause by classifying individuals based on their sex and “transgender status.”

The U.S. Court of Appeals for the Fourth Circuit also said West Virginia’s law violated Title IX of the Civil Rights Act, which prohibits sex-based discrimination in federally funded education.

Two males who identified as female—a middle-schooler named B.P.J. in West Virginia and a college student named Lindsay Hecox in Idaho—had sued to challenge the state’s respective laws.

B.P.J. had been placed on puberty blockers, and argued that the law should not apply to him since he had no biological advantage over girls his age. Hecox made a similar argument, because he had taken female hormones.

The court ultimately ruled that the laws discriminated based on sex—which is permissible when the law is “substantially related” to an important state interest.

Kavanaugh also said the “ongoing medical and scientific debate” about the effect of hormones and puberty blockers on male athletes does not favor the plaintiffs’ argument.

“States and leading athletic organizations disagree with the plaintiffs and have concluded that biological males still retain a physical advantage after taking puberty blockers and hormones,” Kavanaugh wrote.

The three dissenting justices, Sotomayor, Jackson, and Kagan, agreed that the laws discriminated based on sex, not transgender status. They also agreed that B.P.J.’s Title IX claim was not sound.

But they said sex-based discrimination was not justified in this case because the science on hormones and puberty blockers’ effect on male athletes’ advantage is unsettled.

“Because of the Court’s decision today, West Virginia, and any other state actor, can deny B. P. J. and others ... these experiences simply because it thinks they have an inherent athletic advantage, even if the facts show that they do not,” Sotomayor wrote in her dissent.

“In the end, to the Court, the facts do not matter, even though the consequences are serious.”