AT LEAST 12 gay men have been arrested since 2011 for "crimes against nature" under an obsolete and unenforceable anti-sodomy law.

Undercover sheriff's officers in the US city of Baton Rouge have been conducting sting operations against homosexual men, the Baton Rouge Advocate reports.

The suspects were arrested after agreeing to have consensual sex with the undercover officers. No money ever changed hands and the men didn't agree to have sex in public.

There is an anti-sodomy law on the books in Louisiana, which forbids "unnatural carnal copulation by a human being" and "solicitation by a human being of another with the intent to engage in any unnatural carnal copulation".

But the "crimes against nature" law was struck down by the US Supreme Court in 2003, in a ruling which made sexual activity between members of the same sex legal in every state.

For this reason, District Attorney Hillar Moore has refused to prosecute any of the men arrested in Baton Rouge.

Casey Rayborn Hicks, a spokeswoman for the Sheriff's Office, defended the continued application of the unconstitutional law.

"This is a law that is currently on the Louisiana books, and the sheriff is charged with enforcing the laws passed by our Louisiana Legislature," Ms Hicks said.

"The issue here is not the nature of the relationship but the location," she said. "These are not bars. These are parks. These are family environments."

The most recent arrest came after a 65-year-old man agreed to have sex with an undercover officer after being approached in a park.

But attorneys maintain there is no legal basis for the arrests.

"For the Sheriff's Office to be setting these kinds of sting operations up is a waste of time because they can't prosecute these things," defence lawyer Tommy Damico told the Advocate.

Civil rights attorney Andrea Ritchie was more strident.

"It's really unfortunate that police are continuing to single out, target, falsely arrest and essentially ruin the lives of gay men in Baton Rouge who are engaged in no illegal conduct," Ms Ritchie said.

Meanwhile, in Russia, a neo-Nazi group is targeting teenagers who respond to same-sex personal ads on VK.com, the nation's version of Facebook.

Members of the group lure the teens to fake dates, then "bully and even torture them" when they show up, reports The Huffington Post. The encounters are filmed and posted online.

By comparison, a few over-zealous officers in the United States suddenly don't seem quite so bad.

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