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A judge in Tennessee is giving inmates a unique way to reduce their sentences: Have a vasectomy.

The program was issued in May after Judge Sam Benningfield signed a standing order, which permitted inmates to have their sentences shortened by 30 days in exchange for the sterilizing procedure.

Female inmates can also get the birth control implant Nexplanon, which prevents pregnancy for four years, for the same sentence reduction.

The program is voluntary. However, the American Civil Liberties Union of Tennessee has condemned the program, calling it "unconstitutional."

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“Offering a so-called ‘choice’ between jail time and coerced contraception or sterilization is unconstitutional," Hedy Weinberg, ACLU-TN executive director, said in a statement. "Such a choice violates the fundamental constitutional right to reproductive autonomy and bodily integrity by interfering with the intimate decision of whether and when to have a child, imposing an intrusive medical procedure on individuals who are not in a position to reject it."

But Benningfield, who declined to speak to NBC News, told News Channel 5 that he is trying to encourage "personal responsibility" among inmates, who will not "be burdened with children" when they are released.

"This gives them a chance to get on their feet and make something of themselves,” Benningfield told the station.

Since the program began, 32 women have received the birth control implant and 38 men have agreed to have a vasectomy, News Channel 5 reported. It was not immediately clear how many men have undergone the surgery.

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Both options are provided free-of-charge to the inmates, who can also earn an additional two days off their sentences for completing a Tennessee Department of Health Neonatal Syndrome Education Program.

“I understand it won’t be entirely successful but if you reach two or three people, maybe that’s two or three kids not being born under the influence of drugs. I see it as a win, win,” Benningfield said.

The ACLU countered, saying a judge shouldn't play a role in birth control decisions.

"Judges play an important role in our community — overseeing individuals’ childbearing capacity should not be part of that role," Weinberg's statement said.

Glenn Cohen, a professor at Harvard Law School, said the program was a "bad policy," and pointed to prior court rulings, which set a precedent that could make Benningfield's order unconstitutional.

"The approach of this judge is constitutionally questionable. In Skinner v. Oklahoma, the Supreme Court indicated it violated the Constitution to impose sterilization as a punishment for a criminal," Cohen wrote in an email. "This case is slightly different, though, in that it involves sentencing."

Cohen said some states acknowledge that an inmate could waive his or her constitutional rights as a condition of parole, adding birth control is not a topic on which many lower courts have issued rulings.

The ones that have, Cohen said, have been deemed unconstitutional.

"This case seems even more problematic because it seems that some of the birth control mechanisms are permanent/hard to reverse; moreover, a subtle point is that one worries about discrimination here — is the judge allowing women too old to reproduce or individuals that are already infertile to also get this treatment," Cohen said.

Sherry Colb, a law professor at Cornell University, said that although the order might be unfair to those who are sterilized before sentencing, it's not likely that aspect of the program is unconstitutional.

Colb also said while a higher court could deem the program unconstitutional, the judge has immunity from a lawsuit.

In a blog post, the ACLU cited another form of birth control, an implant called Norplant, which has been used as an alternative to jail time for women accused of child abuse or drug use during pregnancy in some states.

In the early 1990s, legislators in more than a dozen states introduced measures to give women the option between birth control and jail, which did not pass. Colb said the Norplant issue set a precedent that could work against Benningfield's program.

The ACLU also argues that this line of logic is unconstitutional and reinforces stereotypes about women in poverty.

"A woman's use of Norplant prevents conception; it does not stop her from taking drugs or abusing her children," the ACLU wrote in a blog post. "The solution to these problems is not forced contraception but adequate drug treatment and social services to prevent and address family violence."

Cohen echoed this point.

"While the judge appears to couch this in 'helping the inmate by not burdening them with extra children' one worries that it actually reflects primitive conception of heritability of criminal behavior, which are roundly rejected by modern day genetics," he said.