This week, Mr. Sessions and the Department of Education rescinded the guidance entirely. His baffling rationale was that it added to the confusion around an issue that has prompted spirited debates and legal fights around the country.

In fact, it did the opposite. Next month, the Supreme Court will hear arguments in the case of Gavin Grimm, a transgender student who has been fighting his Virginia school district for the right to use the boys’ restroom on campus. Under the Obama administration, the Department of Justice took the position that existing federal law already confers that right. Mr. Sessions has reversed the government’s course.

Of all the matters of consequence before the new attorney general, it is curious that Mr. Sessions made repealing this guidance, and abandoning its defense, priorities. He clashed earlier in the week with Education Secretary Betsy DeVos, who reportedly felt uneasy about rescinding the guidelines, a move that will make students vulnerable. After the two made their case to the president, Mr. Trump sided with his attorney general.

This is unsurprising. Mr. Trump has demonstrated time and again that his stated personal convictions are malleable. A genuine champion of gay and transgender rights would have steered clear of politicians like Mr. Sessions and Vice President Mike Pence, who have gone to great lengths to vilify and oppress gay and transgender Americans.

On Wednesday, the White House press secretary, Sean Spicer, justified revoking the transgender school guidance by saying Mr. Trump is a “firm believer in states’ rights.” This inglorious justification has been deployed repeatedly by those on the wrong side of history in earlier civil rights battles. It was used to fight abolitionists, the women’s suffrage movement, the repeal of Jim Crow laws and, most recently, same-sex marriage.