Gov. Asa Hutchinson of Arkansas, a Republican, vetoed an anti-transgender bill. 

Gov. Asa Hutchinson of Arkansas vetoed a bill on Monday that would make it illegal for transgender minors to receive gender-affirming medication or surgery — a rare Republican rejection of the growing conservative effort to restrict transgender people’s health care and participation in society.

The Arkansas State Legislature could override Mr. Hutchinson’s veto of the bill, known as H.B. 1570. Republicans hold large majorities in both chambers and passed the bill last month with mostly party-line votes: 70-22 in the House and 28-7 in the Senate.

“I was told this week that the nation is looking at Arkansas because I have on my desk another bill passed by the General Assembly that is a product of the cultural war in America,” Mr. Hutchinson said in announcing his veto. “I don’t shy away from the battle when it is necessary and defensible, but the most recent action of the General Assembly, while well intended, is off course.”

Chase Strangio, a lawyer at the American Civil Liberties Union who has fought anti-trans legislation in Arkansas and other states, said that while he and other advocates needed to be “tentative in our celebration” because of the possibility of an override, Mr. Hutchinson’s veto was significant both practically and symbolically.

“First and foremost, it’s such an important rebuke of this sweeping range of legislation targeting trans youth across the country,” Mr. Strangio said. Referring to two states that are considering similar bills, he added: “I hope Alabama’s watching. I hope Tennessee’s watching.”

The lead sponsors of the bill — State Representative Robin Lundstrum and State Senator Alan Clark, both Republicans — did not immediately respond to a request for comment.

Republican legislators in numerous states have introduced bills that would restrict transgender rights. In addition to legislation focused on health care, conservatives are pushing bills that would ban transgender women and girls from participating in women’s sports at school.