To be fair, the last Republican administration thought a federal law to deal with this had been passed already when Title IX became law in the early 1970s. Over the next 45 years, every other administration, Republican and Democratic alike, thought Title IX protected fairness and equal opportunity in US education for female students by permitting them/us to have our own separate sports from which all males were automatically barred - along with our own locker rooms and bathrooms that were off-limits to male users as well.
That only began to change during the second term of the Obama presidency when Obama admin officials issued directives saying that from now on, the word "sex" in Title IX should be interpreted to mean students' "gender identity" as well as or instead of their sex. During Obama's second term, the position increasingly taken by the federal government, the Democratic Party and education officials in "blue states" was that when it comes to school restrooms, locker rooms and sports, the claimed gender identities of students who say they are trans, non-binary or otherwise "gender diverse" should override their sex.
Also, education officials in the last Republican administration in Washington did take pretty strong decisive action to deal with the matter of males using gender identity claims to muscle in on female sports when they had the chance.
In May 2020, the US Department of Education’s Office of Civil Rights resolved a complaint filed by female athletes in Connecticut who’d been made to compete against male athletes in girls’ HS track by ruling in the female athletes’ favor. The OCR informed CT state education authorities that they had violated Title IX and deprived the female athletes of their civil rights by allowing males to compete in the female category based on the males’ gender identity claims - and said enforcement actions against them were pending.
The OCR said that “by permitting the participation of biologically male students in girls interscholastic track” the Connecticut Interscholastic Athletics Association and the schools involved had illegally “denied female student-athletes benefits and opportunities” to fair play and full participation in educational programs that are protected by Title IX.
But instead of moving quickly to reconsider and rectify their policy, CT authorities decided to wait to see how the 2020 election turned out. During the campaign, Joe Biden had pledged to rescind the Trump administration’s ruling in the CT Title IX case as that would fit with Biden’s often-stated claim that “trans rights are the civil rights of our time.”
Soon after Biden took office as POTUS, he made good on his promise.
On February 23, 2021 the Biden administration's Department of Education sent the various educational bodies in the Connecticut Title IX case a letter saying that the DoE “hereby withdraws” the earlier findings that CT school authorities had violated the law and the DoE was ceasing enforcement action on the case.
The letter also said that the DoE had told the US Department of Justice it no longer wanted DoJ to initiate judicial proceedings against CT education authorities in the case.