More than 500 college athletes have signed a letter to the NCAA Board of Governors asking the organization to refuse to schedule championships in states that have banned transgender participation in sports.

The move follows a wave of legislative efforts across the country aimed at transgender athletes. The letter to the NCAA asks the board to uphold the organization’s nondiscrimination policy, citing the decision to move championships out of North Carolina in 2016 in response to House Bill 2, which legislated transgender use of public restrooms.

The bills banning transgender participation in sports comes following an anti-discrimination executive order was signed by President Joe Biden in January. The order requires schools not to discriminate based on sexual orientation.

The NCAA, which has permitted transgender athletes to compete in their preferred gender, has rules in an effort to level the playing field. The rules state: “A trans male student-athlete who has received a medical exception for treatment with testosterone for diagnosed Gender Identity Disorder or gender dysphoria and/or Transsexualism, for purposes of NCAA competition may compete on a men’s team, but is no longer eligible to compete on a women’s team without changing that team status to a mixed team.”

“A trans female student-athlete being treated with testosterone suppression medication for Gender Identity Disorder or gender dysphoria and/or Transsexualism, for the purposes of NCAA competition may continue to compete on a men’s team but may not compete on a women’s team without changing it to a mixed team status until completing one calendar year of testosterone suppression treatment.”