Yesterday, the biggest US internet bill in years cleared a major hurdle on the path to becoming law. In a unanimous vote, the Senate Commerce Committee approved the Stop Enabling Sex Trafficking Act (or SESTA), clearing the way for a full vote by the House and Senate. As Congress wrestles over tax reform and the debt ceiling, it’s still unclear when SESTA will reach a larger vote, and it still faces stern opposition from tech policy organizations and even some anti-trafficking groups. But with more than 30 senators already signed on, the bill seems primed to pass whenever it reaches the floor.

The biggest twist has come from the industry itself. After weeks of debate, a string of tech companies and industry groups have come around to supporting SESTA, leaving critics with few allies and narrowing options. It’s an unusual stance for the tech industry to take on a bill that some say would strike at some of the internet’s most fundamental protections. But as Google and Facebook face mounting pressure for regulation, SESTA increasingly seems like a workable compromise, giving prosecutors a new tool while fending off more onerous regulation. For anyone dealing with user-generated content, the result could be a dangerous new source of legal risk, one that only the largest companies are fully equipped to handle.

“Compliance is going to be difficult, especially for smaller platforms.”

First introduced in August, SESTA is designed to make it easier for prosecutors to target websites like Backpage that host ads or otherwise enable sex work. While Backpage was ultimately taken down in a prosecution led by then-California Attorney General Kamala Harris (now a senator), the site’s owners escaped criminal trafficking charges thanks to the protections of Section 230, which prevents sites from being prosecuted for crimes committed by their users. SESTA would change that, explicitly stripping 230’s protections from any platform found to be assisting a sex trafficking enterprise.

But those prosecutions could have dangerous consequences, according to some legal scholars. When the bill was introduced, it was criticized as overly broad; Santa Clara University law professor Eric Goldman said it would “implicate every online service that deals with user-generated content.” The recent Manager’s Amendment to the bill pulled back some of those powers — limiting state lawsuits to a specific sex trafficking statute and narrowing the liability language — but critics haven’t been impressed. Goldman wrote that the change “slightly improves a still-terrible bill.” EFF took a similar line in a post this week, saying SESTA “continues to be a deeply flawed bill.”

The core of the problem is the new burden it would place on anyone hosting content online, and the strong new incentive to ban content before it poses a legal risk. Like traditional anti-piracy measures, SESTA focuses on platforms that provide “knowing assistance” to trafficking ventures. If Twitter gets a tip and doesn’t ban the named account — either because the tip is bad or because the evidence isn’t convincing enough — the message could be used as evidence that the platform knew trafficking was taking place. The result is a strong incentive to ban accounts and a new avenue for malicious reports, and that problem hasn’t changed with recent revisions.

“Just because a big technology company says something is good, doesn't mean it's good for the internet or innovation.”

“Compliance is going to be difficult, especially for smaller platforms,” says Emma Llansó, director of the Free Expression Project at the Center for Democracy and Technology. “When intermediaries aren’t sure what will get them into legal trouble, we often get broader content filtering that sweeps in a lot of legitimate content.”

That’s a particular problem for smaller networks that won’t have the legal resources of Google or Facebook, a concern raised by Sen. Ron Wyden (D-OR). “After 25 years of fighting these battles,” Wyden said in a statement, “I’ve learned that just because a big technology company says something is good, doesn't mean it's good for the internet or innovation. Most innovation in the digital economy comes from the startups and small firms, the same innovators who will be harmed or locked out of the market by this bill.”

But while the legal concerns remain, the revision has won over powerful new support from the tech industry. Last week, the bill gained a pivotal endorsement from the Internet Association, a trade group supported by Google, Facebook, Microsoft, and others. The association had opposed the bill when it was first introduced, but said the recent changes were sufficient to “protect good actors in the ecosystem.”

“A regulatory structure that only the largest companies can really navigate.”

Big tech companies have mostly fallen in line behind the association. Facebook has been the most open in its support, with chief operating officer Sheryl Sandberg applauding the most recent version of the bill. “Thank you to lawmakers in both parties – particularly Senators Portman and Blumenthal,” Sandberg wrote in a post on Tuesday. “As this moves through the House and Senate, we’re here to support it.”

Old Google rivals like Oracle and 21st Century Fox have come out loudly in support of the bill, but Google’s own stance is more complex. The company expressed mild concerns about SESTA before the revisions, but has changed course in recent weeks. Reached by The Verge, a Google representative said the company had “nothing to add beyond the Internet Association’s statement from last week.”

It’s hard to say what’s behind the recent change of heart. With the Russia hearings still fresh, and Sen. Al Franken (D-MN) already calling for more checks on their power, Google and Facebook’s sway in Washington is lower than ever. It may be that the companies aren’t eager to fight a sex trafficking bill on top of everything else, and see Portman’s compromise as the best they’re likely to get. At the same time, critics say the bulk of the damage is likely to fall on smaller firms without the legal resources of the established companies.

“It’s the kind of thing larger platforms might already be able to deal with, but I can’t imagine the same goes for startups,” says Llansó. “Overall, my worry is that this would push us towards a regulatory structure that only the largest companies can really navigate.”