MONTGOMERY, Ala. — Some Alabama sex offenders who abuse young children will have to undergo “chemical castration” while on parole, under a new law, but the requirement has prompted legal concerns and appears to be rarely used in some states that allow it.

The procedure uses medications that block testosterone production in order to decrease sex drive. The Alabama law says sex offenders whose crimes involved children between the ages of 7 and 13 must receive the medication before being released from prison on parole. Alabama doesn’t allow parole for sex crimes involving children 6 and under.

After Gov. Kay Ivey’s office announced last week she had signed the bill, some legal groups raised questions.

Randall Marshall, executive director of the American Civil Liberties Union of Alabama, said there are constitutional concerns with forced medication.

Dillon Nettles, a policy analyst with the ACLU of Alabama, said the law harkens back to a “dark time” in history.

The bill’s sponsor, Republican Rep. Steve Hurst of Munford, scoffs at that kind of talk.

“How in the world can it be any more cruel and inhumane than to molest a child? I want someone to answer that one for me, but they can’t,” Hurst said.

Hurst said he hopes the medication will protect children by stopping abusers from reoffending.

At least seven states have laws authorizing chemical castration in some form.

The hormonal treatment can be useful for a subgroup of offenders whose crimes are driven by sexual attraction to children and want to reduce those urges, said Dr. Frederick Berlin, who treats patients with sexual disorders at Johns Hopkins Hospital and at an independent clinic. However, he said it’s not effective for people whose crimes were driven by drugs, mental illness or other issues.