A new bill that aims to protect victims of sex trafficking and clamp down on the practice online has garnered support from a broad coalition of lawmakers in both chambers of Congress.

But the legislation's supporters are up against tech industry leaders in Silicon Valley, who are pushing back on the measure because of the changes it makes to a 21-year-old law protecting online speech.

The legislation, called the Stop Enabling Sex Trafficking Act, or SESTA, was the result of a two-year investigation by Sen. Rob Portman, R-Ohio, into Backpage.com, a website where victims of sex trafficking are sold.

Portman introduced SESTA in the Senate last month. The bill would amend Section 230 of the Communications Decency Act, so websites that facilitate sex trafficking could be held liable. SESTA also allows for civil suits related to sex trafficking.

The bill already has 27 Republican and Democratic cosponsors, and the Senate Commerce Committee will hold a hearing on the measure Tuesday. A similar bill introduced in the House by Rep. Ann Wagner, R-Mo., in April has more than 115 cosponsors from both parties.

SESTA also is backed by victims advocacy organizations, attorneys general from 48 states, the District of Columbia, and Puerto Rico, social conservative groups such as the Family Research Council and the Faith and Freedom Coalition, and the National District Attorneys Association, to name a few.

Although various parties agree that the bill's goal of curbing sex trafficking and protecting victims is commendable, technology companies and tech experts are worried about the impact the legislation will have on future innovation and free speech on the Internet.

"It's being pitched as a narrow fix, ‘We're only talking about sex trafficking. Only targeting the bad platforms,'" Aaron Mackey, a staff attorney at the Electronic Frontier Foundation, told the Washington Examiner. "It's important to think about what Section 230 does and what it would open up. … What I worry about isn't Facebook or Google's ability to comply, but it's what does that mean for the next set of innovators, for people thinking about how to organize online and in different ways."

Under Section 230, online entities can't "be treated as the publisher or speaker of any information provided by another information content provider."

The Electronic Frontier Foundation heralds Section 230 as the "most important law protecting Internet speech," and the organization and technology trade associations warn SESTA could lead online entities to police user content.

"Without this crucial protection, these service providers would err on the side of removing their users' content or face unsustainable liability for their users' content that would harm the creation of legitimate diverse online services," according to a letter written by 10 tech trade associations, including the Internet Association and the Computer and Communications Industry Association, to Portman and Sen. Richard Blumenthal, D-Conn., SESTA's main Democratic cosponsor.

But the consequences, Mackey warned, extend beyond the big players that have developed over the 20 years since Section 230 was enacted.

Because SESTA would allow for criminal proscutions and civil suits against web companies hosting content that violates federal and state trafficking laws, Mackey said web companies are going to need a "team of lawyers" with knowledge of all state and federal trafficking laws that could make them subject to lawsuits or criminal prosecutions.

"What people have said is the Googles, Facebook, Twitter can all afford a small army of lawyers to deal with this," Mackey said. "But I think what about the next Google or the next Twitter or the next Facebook that is a small company that's trying to innovate or create new types of ways to interact online?

"That's the bottom line of what Section 230 was about. It was created so anyone had an opportunity. Having a small startup create an Internet platform that might some day be the next big thing, it's untenable for them to have a small army of lawyers, when they might not even have one."

Also at issue for the tech industry is the precedent SESTA could set for future changes to Section 230.

Eric Goldman, a law professor at Santa Clara University School of Law and co-director of its High Tech Law Institute, said the bill could become a template for future regulatory efforts that don't relate to sex trafficking, such as terrorism.

Internet companies cannot now be held liable for terrorist content users post or share, and social media companies have used Section 230 as their defense when sued by families of victims of terrorism.

"Assume for a moment that the goal is to help the victims of sex trafficking have a civil claim," Goldman, who is scheduled to testify Tuesday, told the Washington Examiner. "You can imagine other victims advocacy groups saying, ‘What are we? What about us? Why did you privilege that class of crimes and not us?' The answer then is you get your due as well."

Portman has sought to ease the concerns of Internet companies and tech advocates who worry SESTA could harm online speech and threaten not only today's platforms, but future ones.

"This bill will allow victims to get justice … and will do so in a way that protects Internet companies that are doing the right thing," he said during a floor speech. "Notably, we preserve the Communications Decency Act's Good Samaritan provision, which protects those good actors who proactively block and screen for offensive material, shielding them from any possibility of frivolous lawsuits.

"That's important. The good actors out there and the vast majority of websites are good actors, have nothing to do with sex trafficking. In fact, many of them police their site for it. The Facebooks of the world, the Googles of the world, they are not the bad actors."

Plus, Portman's office said those involved in the bill's drafting reached out to the broader tech community — both individual companies and trade associations — for input while working on it.

"We had an open dialogue with the tech community for months," Kevin Smith, spokesman for Portman, told the Washington Examiner. "We did our due diligence with them. They had the text of the bill for months. … It is our view that our bill doesn't impact the good actors out there at all. Our bill is a very narrow carve-out. It says that if a website is actively facilitating the promotion of online sex trafficking, then they can be held accountable. No one believes these tech companies that you're talking to on a daily basis are doing that, so we think their claims about our bill are absurd and laughable."

Sen. Ron Wyden, D-Ore., however, is concerned the sex-trafficking bill could lead to "endless lawsuits" for Internet companies, despite their best efforts to police platforms.

Wyden introduced the amendment that would become Section 230 with former Rep. Chris Cox, R-Calif, while serving in the House.

"Section 230 of the Communications Decency Act is widely viewed as the legal basis for all of social media, and it has been vital to the expansion of affordable Internet access throughout the country," he said. "This proposal takes a wrecking ball to that foundation without so much as a committee hearing. It is yet another example of the technical ignorance of Congress threatening the jobs, lives and economic opportunities of millions of Americans."

Though leaders in Silicon Valley are pushing back against SESTA, Oracle came out in support of the measure last week and attempted to quiet the concerns raised by its fellow online entities.

"We are 100 percent confident that a Portman/Blumenthal amendment — identical to S. 1693 — offered to the Communications Decency Act in 1996 would have passed the Senate overwhelmingly and the Internet would have enjoyed the same exponential growth and innovation over the past twenty one years," Ken Glueck, senior vice president at Oracle, wrote in a letter to Portman and Blumenthal. "Frankly we are stunned you must even have this debate."

21st Century Fox also backed the bill. Portman is expecting more tech companies to follow suit, Smith said.

"We will have strong support from the tech community for this bill, and we obviously will be very happy to receive that support," he said.