An Idaho law that bars transgender athletes from playing sports is being challenged.

The first-in-the-nation law was signed by Republican Governor Brad Little two weeks ago with little fanfare and has yet to go into effect.

Titled the “Fairness in Women's Sports Act,” the bill, House Bill 500, bans transgender women and girls from playing on female high school and college sports teams. The legislation applies to all publicly sponsored sports teams.

Supporters of the bill said that it is needed because transgender women and girls have a physical advantage. Opponents argued that the bill subjects transgender athletes to invasive tests.

On Wednesday, a coalition of legal groups – the ACLU, the ACLU of Idaho, Legal Voice, and Cooley LLP – filed a lawsuit on behalf of a track athlete at Boise State University who is transgender and a junior at Boise High School who is cisgender.

“We're suing because HB 500 illegally targets women and girls who are transgender and intersex and subjects all female athletes to the possibility of invasive genital and genetic screenings,” Gabriel Arkles, senior staff attorney with the ACLU's LGBT & HIV Project, said in a statement. “In Idaho and around the country, transgender people of all ages have been participating in sports consistent with their gender identity for years. Inclusive teams support all athletes and encourage participation – this should be the standard for all school sports.”

Plaintiff Lindsay Hecox, the BSU transgender student who hopes to join the school's track and cross country teams, said: “I just want to run with other girls on the team. I run for myself, but part of what I enjoy about the sport is building the relationships with a team. I'm a girl, and the right team for me is the girls' team.”

Lawyers for the plaintiffs argue that Idaho's law violates the Equal Protection Clause of the Fourteenth Amendment of the U.S. Constitution and Title IX, which prohibits discrimination in schools on the basis of sex.