Idaho’s Republican senators are opposing a proposed Biden administration rule that would allow transgender students to compete on sports teams consistent with their gender identity.

Sens. Mike Crapo and Jim Risch co-signed a letter which said the proposal undermines Title IX, the landmark federal education law banning discrimination on the basis of sex.

“By pushing a political agenda which completely ignores science and extending these protections to biological males, the department is intentionally erasing opportunities and progress made by women in the last 50 years,” reads the letter, co-signed by 18 other Republican senators.

In a news release, Risch said the rule ignores “clear biological differences between women and men (and) girls and boys.”

Said Risch: “The Biden administration’s endorsement of biological men playing women’s sports hurts America’s daughters and granddaughters.”

In the same release, Crapo said, “Our female athletes have dedicated countless hours and resources to excel in their chosen sports and are now being sidelined by biological males competing in women’s sports.”

The rule, proposed in April, would prohibit K-12 schools, colleges and universities from imposing a blanket ban applying to all transgender athletes.

But the rule allows for exceptions.

According to a U.S. Department of Education fact sheet, the proposal “would allow schools flexibility to develop team eligibility criteria that serve important educational objectives, such as ensuring fairness in competition or preventing sports-related injury.”

More details on the proposal from Chalkbeat.