The Seattle Public Schools Board of Directors is poised to vote Monday on whether to authorize “legal action” regarding Initiative 638, which requires girls to prove their “biological sex” to play girls’ sports.

Fifty-six percent of Washington state voters approved the measure. Under the new law, girls will have to undergo a genital check, take a hormone test for testosterone levels, or submit to a chromosome test, according to the initiative’s language.

Board President Gina Topp told KUOW Sunday that it’s unclear if the initiative is legal.

“There’s some confusion here about how and if the law is legal,” Topp said. “When that happens, I think we have a duty as a school board to seek the clarification we need in order to govern.”

Topp told KUOW that the resolution would give Superintendent Ben Shuldiner and the district’s legal counsel permission to pursue legal action.

In September, the board unanimously adopted a resolution opposing the passage of Initiative 638.

Currently, the Gender Justice League, a progressive advocacy group in Washington state, is also considering legal action over the initiative. The initiative reverses a previous policy that had allowed students to play on teams that matched their gender identity, going back to 2007.

Supporters of the measure have said that the initiative would address fairness and safety in girls’ sports. Brian Heywood, a conservative hedge fund manager and founder of the political action committee Let’s Go Washington (which backed the initiative) has said the new rules won’t change existing medical requirements for students. But questions around enforcement remain.

The board meeting will be held at 6:30 p.m. Monday at the John Stanford Center.