JEFFERSON CITY, Mo. — Top law enforcement officers across the country are pushing Congress for greater authority to go after a booming online industry that hosts ads for child sex traffickers.

But they are encountering opposition from an unexpected source — conservative state lawmakers who fear a government clampdown on Internet businesses.

The conflict highlights the difficulty of policing an online marketplace that has rapidly evolved under a generally hands-off approach by government.

A coalition of conservative lawmakers and businesses has drafted a model resolution that could be considered next year in state capitals from coast to coast. The document urges Congress to deny state prosecutors the enforcement power they seek over the ads — warning that it could discourage investment in new Internet services.

For state lawmakers wary of being characterized as sympathetic to sex offenders, it’s admittedly a political risk.

“Obviously, anything dealing with sexual predators or sex trafficking, we want to put an absolute stop to that,” said North Dakota state Rep. Blair Thoreson, a Republican who leads a multi-state task force opposing the request by state attorneys’ general. “But in this case, I think we can maybe find other ways to do it.”

Some attorneys general say the concerns are unfounded.

“It’s not like we’re trying to hurt free speech. We’re trying to protect children who are being sold for sex,” said Georgia Attorney General Sam Olens, a Republican.

Of particular concern to state attorneys general are online classifieds, such as those hosted by Backpage.com, which advertise “adult” services for strippers and escorts with veiled references to prostitution. Investigators say that pimps offering children are using the sites, making it easier for pedophiles to buy sex.

Prosecutors have brought charges against pimps, prostitutes and customers who have advertised on Backpage. But they have been precluded from pursuing the website itself because of a 1996 federal law that generally shields website operators from liability for content posted by users.

Last month, a U.S. district judge blocked a New Jersey law against advertising sexual services by minors. Judges in Tennessee and Washington have issued similar rulings.

Frustrated by such failures, 47 state attorneys general signed a letter this summer to the leaders of the U.S. House and Senate commerce committees urging them to make a two-word tweak to the federal law to allow the prosecutions. Congress has yet to act.

When “corporations are knowingly generating revenue from what is widely or universally viewed as criminal conduct, the (federal law) should not stand as a shield for corporate revenues,” said Missouri Attorney General Chris Koster, a Democrat who was the lead signatory of the letter.