Montana Governor Greg Gianforte, a Republican, on Friday signed a bill that restricts gender-related medical care for transgender youth.

According to the AP, at least 15 states have such a law.

The signing comes after state Representative Zooey Zephyr, Montana's first transgender lawmaker, was silenced by Republicans for her opposition to the bill.

GOP leaders acted after Zephyr told her fellow lawmakers that they would have blood on their hands if the bill became law. Her silencing led to protests and arrests in the House chamber.

“I know that this is an unconstitutional bill. It is as cruel as it is unconstitutional. And it will go down in the courts,” Zephyr said after Gianforte gave his approval.

The bill is expected to take effect on October 1 but civil rights groups have said that they will file a legal challenge.

The Human Rights Campaign (HRC), the nation's largest LGBTQ rights advocate, criticized Gianforte, calling him an “extremist.”

“Governor Gianforte is an extremist, and the last thing he cares about is the well-being of transgender kids,” the group's Cathryn Oakley said in a statement. “This bill prevents certain kids from getting potentially life-saving health care simply because those kids are transgender – and that’s discrimination. Montana families deserve so much better.”

Under the legislation, medical professionals who provide such care to minors could have their medical licenses suspended for at least one year. It also allows patients to sue providers and prohibits the use of public resources for such treatments.