NASHVILLE, Tenn. (AP) — Tennessee Gov. Bill Lee signed a law Friday banning transgender athletes from participating in girls’ sports, making it the third state this year to approve a measure many critics warn would prompt costly lawsuits and hurt transgender youth.

The Republican governor said on his Twitter account that he signed the bill “to preserve women’s athletics and ensure fair competition.” Mississippi and Arkansas have approved similar laws, and Republicans in at least 20 state legislatures have been pushing for transgender athlete bans this year.

Tennessee’s Republican-led Legislature gave final approval to the bill after House lawmakers voted 71-16 for the bill after little debate on Monday.

According to Tennessee’s bill, student athletes would be required to prove that their sex matches that listed on the student’s “original” birth certificate in order to participate in public school sports in middle and high schools. If a birth certificate is unavailable, then the parents must provide another form of evidence “indicating the student’s sex at the time of birth.”

Backers of the bill argue that transgender girls, because they were identified as male at birth, naturally are stronger, faster and bigger than those identified as female at birth and therefore have an unfair advantage in sports.

Lee has said transgender athletes would “destroy women’s sports” and remarked that transgender athletes would put “a glass ceiling back over women that hasn’t been there in some time.”

None of the supporters of the Tennessee measure could cite a single instance of transgender girls or boys having caused problems. A review by The Associated Press found only a few instances in which it has been an issue among the hundreds of thousands of American teenagers who play high school sports.

Opponents counter that such proposals violate Title IX of federal education law prohibiting sex discrimination, as well as rulings by the U.S. Supreme Court and 11th U.S. Circuit Court of Appeals. Others point to an executive order signed by Democratic President Joe Biden that prohibited discrimination based on gender identity in school sports and elsewhere.

Legislation previously enacted in Idaho has never been implemented after it was blocked by a federal judge while a lawsuit proceeds in court.

Democrats in the Tennessee General Assembly have said the law is about discrimination, not fairness in sports.

The American Civil Liberties Union of Tennessee decried the bill as “shameful” after House passage, arguing that transgender girls do not threaten women’s sports.

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