If the bill passes, it'll mean that a website can't use safe harbor rules if it "knowingly" aids in sex trafficking, a la Backpage's sex listings.

The Electronic Frontier Foundation (EFF) has been fighting the bill, saying that it will actually undermine law enforcement efforts to combat trafficking. The EFF argues that taking these sites offline would eliminate venues for apprehending johns and purveyors of underage sex.

There's also a worry that the senate bill and a similar House bill (Allow States and Victims to Fight Online Sex Trafficking Act; FOSTA) passing could harm free speech. The concern is this could lead to a crackdown on posts for any type of sex work, "regardless if there's any indication of force or coercion, or whether minors were involved," the advocacy group wrote in December.

"Like SESTA, the proposed new FOSTA bill would result in platforms becoming more restrictive in how they manage their online communities," it said. "And like SESTA, it would do nothing to fight sex traffickers."

SESTA's main supporters, Senators Rob Portman (R-OH) and Richard Blumenthal (D-CT) are urging colleagues for quick passage. The senators would like to see the bill become law as soon as possible given that the president named January National Slavery and Human Trafficking Prevention Month this week.