The US Supreme Court has ruled that states can ban transgender women from competing in female school and college sports.

The court considered cases from students in two different states who had challenged bans on participation. The two states, Idaho and West Virginia, enacted laws that required public school and college sports teams to compete in accordance with their sex recorded at birth.

One of the two challenges says the ban violates equal rights protections in the US Constitution. The other says it contradicts civil rights laws.

More than two dozen states have enacted bans since Idaho did so in 2020.

Under those state bans, a transgender woman – a biological male who identifies as a woman – is not permitted to compete in female sports at schools and colleges.

All nine justices on the court decided the state bans do not violate a civil rights law called Title IX which prohibits sex-based discrimination in schools.

But the judges were split along ideological lines on whether the bans contravene the constitution’s 14th Amendment guarantee of equal protection under the law.

The six conservative justices said it did not violate the constitution but the three liberal justices disagreed.

“The Constitution and Title IX do not require an overhaul of women’s and girls’ sports throughout America,” wrote Justice Brett Kavanaugh who authored the ruling.

In her partial dissent, Justice Sonia Sotomayor said the majority opinion had applied “a diminished view of equal protection” to sports.

The challenge launched in Idaho came from Lindsay Hecox, a long distance runner, who lodged it shortly after the law was enacted. She was later granted an injunction by both a district court and an appeals court.

State lawmaker Barbara Ehardt, who introduced the law, said at the time of its passing that it would ensure “boys and men will not be able to take the place of girls and women in sports because it’s not fair”.

But in the appeals ruling, a panel of three judges found that the Idaho law violated constitutional rights. They said the state had failed to provide evidence that its ban protects “sex equality and opportunity for women athletes”.

President Donald Trump made the issue of transgender athletes in women’s sports a regular focus of his 2024 election campaign. Last year, he signed an executive order that aimed to ban transgender women from competing on female sports teams.

Following that decision, the NCAA, the governing body for US college sports, banned transgender women from competing in women’s sports.

Supporters of the bans argued that transgender women had a biological advantage over athletes who were recorded female at birth.

When the International Olympic Committee (IOC) announced in March it was going to limit the women’s category of Olympic sports to biological females, it said its working group reviewed the latest scientific evidence over the previous 18 months and had concluded there was a “clear consensus”, external that “male sex provides a performance advantage in all sports and events that rely on strength, power and resistance” .

Those who opposed the bans argue that they unfairly discriminated against transgender students and dispute whether there is a scientific consensus that transgender women and girls have an inherent advantage.