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. Idaho banned transgender women from taking part in women’s and girls’ sports last year, although that law has been challenged in court. State legislatures in North Dakota and Mississippi have recently passed similar measures.

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.

“We call upon you to ensure that the NCAA lives up to the guidelines and standards that they claim to uphold by making a firm statement that you will uphold the NCAA Anti-Discrimination Policy and only operate championships and events in states that promote an inclusive atmosphere,” the letter says.

The NCAA has had policies in place since 2011 that allow for transgender participation in sports.

The letter was the idea of track and field athletes Aliya Schenck and Alana Bojar of Washington University in St. Louis, who work with Athlete Ally. Athletes from across the different college sports signed on to the effort.

“All student-athletes should be safe and protected when competing in NCAA championships,” the two said in a statement. “Your silence on this issue is only allowing more states to pass these bills. We urge you to act now and make a strong statement against these bills, saying that the NCAA will not host championships in states that openly discriminate against LGBTQI+ athletes.”

Athlete Ally is a nonprofit group that advocates for LGBTQI+ athletes. Last year it was part of an effort on behalf of 200 current and former athletes — including Megan Rapinoe, Billie Jean King and Candace Parker — who filed an amicus brief with the 9th U.S. Circuit Court of Appeals in opposition to the Idaho law.

“Though the NCAA has continued to monitor the bills and has spoken out in support of trans athletes, the time is now for the NCAA to listen to hundreds of student athletes calling on them to clearly and unequivocally put the health and safety of all student-athletes first and condemn these horrific bills,” said Anne Lieberman, Athlete Ally’s director of policy and programs.

The NCAA issued a statement to The Associated Press saying it continues to monitor legislation that affects transgender athletes.

“The NCAA believes in fair and respectful student-athlete participation at all levels of sport. The Association’s transgender student-athlete participation policy and other diversity policies are designed to facilitate and support inclusion,” the statement said. “The NCAA believes diversity and inclusion improve the learning environment and it encourages its member colleges and universities to support the well-being of all student-athletes.”