This month, Washington lawmakers overwhelmingly passed a narrow bill that seeks to crack down on sex trafficking online. To most, it seemed like a no-brainer: Sex trafficking is obviously bad. The law, however, changed Section 230 of the Communications Decency Act of 1996, a 20-year-old communications law that is the basis of the free internet as we know it.

On April 11, President Donald Trump signed the bill — a combination of bills passed by the House and Senate, the Allow States and Victims to Fight Online Sex Trafficking Act (FOSTA) and the Stop Enabling Sex Traffickers Act (SESTA) — into law.

The legislation opens more avenues for victims of online sex trafficking to legally pursue websites that facilitate trafficking by amending Section 230, making it easier for federal and state prosecutors and private citizens to go after platforms whose sites have been used by traffickers.

FOSTA-SESTA, however, isn’t without its detractors: Some sex workers say it will actually put them in further danger and push illicit activity into even deeper corners of the internet, and free internet proponents worry that platforms might censor or pull content preemptively just to avoid risk.

FOSTA-SESTA was particularly aimed at Backpage.com, a website that has long been known for its sex worker advertisements, but it has made a number of platforms nervous. Multiple websites have censored or banned parts of their platforms preemptively, not necessarily because the sites were promoting ads for prostitutes, but because policing them under the new law would be too hard. Federal authorities took down Backpage before FOSTA-SESTA was actually signed.

Section 230, however, presents a broader issue in the context of FOSTA-SESTA than meets the eye. The law creates an exception to Section 230 that means platforms would be responsible for third-party content related to sex trafficking or conduct that “promotes or facilitates prostitution.” (Vox’s Aja Romano has a complete explainer on the bill.)

Originally, Section 230 was intended to shield tech platforms from liability for content posted by their users. It treats internet companies like libraries: A library isn’t responsible for the content of the books it carries. The bill was co-authored by former Republican Rep. Chris Cox (CA) and Democratic Sen. Ron Wyden (D-OR) and was received as a forward-thinking principle that would help shape the growth of the then-nascent internet. Beyond the legislation itself, FOSTA-SESTA has also spurred speculation that more attempts to poke holes in Section 230 may be on the horizon.

The statute has been lauded as a “core pillar of internet freedom” and “the most important law protecting free speech online” that “gave us the modern internet.” But it has become more and more imperiled, not only with FOSTA-SESTA but also in light of increased scrutiny on Facebook and the advent of platforms such as Airbnb and Yelp, where third-party content is the business model.

“I think 230 is going to be the central discussion point for the next two to five years on what the internet looks like,” one congressional aide told me.

Despite concerns, FOSTA-SESTA passed Congress pretty easily. It flew through the Senate on a 97-2 vote, with just Wyden, one of Section 230’s authors, and libertarian Sen. Rand Paul (R-KY) voting against it. A number of high-profile celebrities spoke out in favor of the bill, including actress Amy Schumer and late-night comedian Seth Meyers, who took part in a public service announcement supporting it.

“Ultimately, what we saw is that it is politically almost impossible to do anything but support a bill that says it will stop child sex trafficking,” Emma Llanso, director of the Center for Data & Technology’s (CDT) free expression project, told me.

Ever seen The Wolf of Wall Street? That’s where Section 230 comes from.

Section 230 was born from a couple of 1990s court cases that decided whether tech companies at the very beginning of the internet were responsible for what people were sharing on the platforms they had created.

In 1991, the US District Court for the Southern District of New York ruled in Cubby Inc. v. CompuServe Inc. that CompuServe, the United States’ first major commercial online service provider, wasn’t liable for hosting defamatory content on one of its forums after a columnist posted negative comments about a competitor.

Four years later, in 1995, a new court case popped up, this time involving Stratton Oakmont, the investment firm featured in the 2013 film The Wolf of Wall Street. When chatter on a forum hosted by Prodigy Services popped up that Stratton Oakmont was up to criminal activity, the firm sued. And in Stratton Oakmont Inc. v. Prodigy Services Co., the New York Supreme Court decided the online host was indeed liable for the content posted there.

The argument: Prodigy was moderating its online message boards and deleting some messages, while CompuServe was acting like a blind host, not touching anything. And so legislators saw a need for a clear law to outline what the then-blossoming internet ecosystem was and wasn’t responsible for.

They found their opportunity in the Communications Decency Act, a 1996 law intended to regulate pornographic material, obscenity, and indecency online. Much of the act was struck down in 1997, when the Supreme Court held that it violated the First Amendment’s free speech guarantee. But Section 230, which had been added as an amendment to the law by Cox and Wyden (initially proposed as an alternative to it), survived.

“It was intended as the right way to ensure that platforms could maintain healthy and strong community standards while not restricting people’s civil liberties online,” said Elliot Harmon, an activist at the Electronic Frontier Foundation (EFF), a nonprofit organization focused on civil liberties in the digital space.

The statute declares that “no provider or user of an interactive computer service shall be treated as a publisher or speaker of any information provided by another information content provider” — in other words, tech companies aren’t responsible for what users put on their platforms. On the flip side, it also ensures companies have the space to police their own sites and restrict or take down material they consider obscene, violent, or otherwise objectionable. But platforms can’t wash their hands entirely — federal criminal laws apply, and there are carve-outs for arenas such as intellectual property.

“It’s basically the fundamental framework for how we think about the legal liabilities of intermediaries around user-generated content,” said Llanso, from the CDT.

The tech community views Section 230 as one of the most important principles of the internet.

“Intermediary liability protections are fundamental to the internet — for both consumers and the internet sector,” said Michael Beckerman, president and CEO of the interest group the Internet Association, adding that they “enable virtually all user-generated content online.”

FOSTA-SESTA might be a one-time deal in terms of amending Section 230. The fear is it’s just the beginning.

There are concerns that FOSTA-SESTA could lead to the further erosion of internet freedom and safe harbor protections. “The larger question is whether this is part of a case for more extensive regulation on different intermediaries, and I think we just don’t know the answer to that yet,” said Harvard law professor Rebecca Tushnet.

Multiple lawmakers touted the bill at Facebook CEO Mark Zuckerberg’s appearance at a joint hearing of the Senate Judiciary and Senate Commerce committees in April. Zuckerberg testified before the joint Senate committee hearing and a hearing before the House Energy and Commerce Committee about a wide range of issues, including data privacy, content handling, and its business practices.

Sen. John Thune (R-SD), chair of the Commerce Committee, said the bill “should be a wake-up call for the tech community” and seemed to open the door to more action. “We want to hear more, without delay, about what Facebook and other companies plan to do to take greater responsibility for what happens on their platforms,” he said.

Sen. Ted Cruz (R-TX) brought up Section 230 direction in the context of inquiring whether Facebook has a liberal bias. “The predicate for Section 230 immunity under the [Communications Decency Act] is that you’re a neutral public forum,” Cruz said. “Do you consider yourself a neutral public forum, or are you engaged in political speech, which is your right under the First Amendment?”

Many lawmakers, especially in the Senate, appeared confused about what Facebook does, exactly what problems they wanted to fix about it, and how they might begin to regulate it. It is also worth noting that US lawmakers have historically been reluctant to regulate technology, as opposed to Europe, which has been much more aggressive.

“There have clearly been some obvious threats that members of Congress want to do something like FOSTA-SESTA for terrorist content or for hate speech,” said Harmon, from the EFF. “That’s clearly been a theme that has come up again and again: How can Congress shift more liability onto platforms to have them spend more time policing their users’ speech? That is definitely a concern, and I wouldn’t be surprised if you start seeing bills like that.”

Others say internet freedom advocates who have expressed alarm about a Pandora’s box of Section 230 attacks are getting out over their skis. “When you look at the original purpose of Section 230, I think this amendment is very minor and is not a boding of things to come,” said Mary Leary, a law professor at Catholic University. “Everyone agrees that Section 230 was never intended to provide this kind of protection to companies that were engaged in sex trafficking.”

In September, Oracle wrote a letter supporting FOSTA-SESTA, saying the state of technology today makes monitoring content easier than it was in the 1990s and expressing surprise at the debate over the legislation. “Your legislation does not, as suggested by the bill’s opponents, usher the end of the internet,” wrote Oracle senior vice president Kenneth Glueck. “If enacted, it will establish some measure of accountability for those that cynically sell advertising but are unprepared to help curtail sex trafficking.”

The Internet Association, an internet industry lobbying group, initially lobbied against FOSTA-SESTA but backed off in September and then came out in support of the Senate bill, citing “important changes” made to the legislation. (It is worth noting it did so days after officials from Facebook, Google, and Twitter testified on Capitol Hill about Russian meddling in the 2016 election.)

What happens next might depend on how FOSTA-SESTA plays out and what it actually affects about the internet — though there have already been some casualties. Craigslist removed its entire personals section from its platform two days after SESTA’s passage in the Senate, citing the difficulty of adhering to new changes to the law; Reddit banned multiple subreddits; VerifyHim, a screening site for online dating that sex workers use to verify clients, shut down its advertising “newsreel”; Microsoft, which owns Skype and Xbox, has banned “offensive language.” Backpage, a Craigslist-type site that had a controversial sex work section, was shut down and seized by the FBI before FOSTA-SESTA became law.

N’jaila Rhee, an educator and sex worker who hosts The Cuntcast Podcast, said the closures and bans are making sex workers less safe, not more. Instead of being able to vet their clients and make their own decisions about where and when to work and with whom, it pushes them toward intermediaries who find clients for them — but take away the choices they can make when working on their own.

“It seems mostly it’s avenues being closed for sex workers that want to work independently and safe,” she said. “People who are used to working independently now are trying these more dangerous avenues of working, and they have no experience in doing so.”

Some sex workers have turned to Switter, a sex community-friendly social network hosted in Australia, but its future is uncertain. The corporate internet security software company Cloudflare banned Switter last week because of FOSTA-SESTA, which Cloudflare told Motherboard is a “very bad law.” (Cloudflare previously banned the neo-Nazi website the Daily Stormer.)

FOSTA-SESTA is perhaps especially bad for some of the most vulnerable sex workers already, namely, transgender and undocumented people, Rhee said. “I don’t see this as any different than the war on drugs, if we can admit that that was racist hogwash,” she said. “The criminalization of sex work is here to target women, target transgender people, target gay people.”

What’s next for Section 230 is up in the air

There’s no question that Section 230 is one of the pillars of the open internet. Along with net neutrality, it helps level the playing field in tech by allowing new entrants to get into the market without huge barriers.

Eroding Section 230 and increasing companies’ liabilities for content shared on their platforms by their users is likely to ding small players and new startups — not the mega companies such as Facebook, Google, and Twitter. They have billions of dollars, lobbyists, and extensive legal resources behind them.

“Laws that require automated filtering of content and other types of moderation at scale might be something a giant platform could handle, but it could make it very difficult for a smaller competitor or startup to be successful,” Llanso, from the CDT, told me.

In his testimony before the joint Senate committees and the House Energy and Commerce Committee last week, Zuckerberg said that Facebook is “responsible for the content” on its platform — though it’s likely he was speaking of a moral responsibility, not a legal one.

“One of the best ways to ensure that Facebook faces no further competition is to put extensive regulations on companies that do what Facebook does, because Facebook is the only one with billions of dollars of revenue that it can put into satisfying these requirements,” said Tushnet, the Harvard law professor.

In the end, the questions about the future of Section 230 revolve around whether we believe the internet in its current form is worth preserving — whether it should be open, free, a place for dissent — or whether it’s grown into a jungle of ideas and information that needs to be put under control.

The US has traditionally been a leader in the tech industry; it is the birthplace of the biggest companies and many of the most important innovations in the world, in large part because of principles such as Section 230 and net neutrality, which help level the playing field and spur growth. And free speech under the First Amendment is a basic American value.

Perhaps one of the best arguments for Section 230 is laid out in one of the first major federal court cases to discuss it, Zeran v. America Online Inc., in 1997:

Whenever one was displeased with the speech of another party conducted over an interactive computer service, the offended party could simply “notify” the relevant service provider, claiming the information to be legally defamatory. In light of the vast amount of speech communicated through interactive computer services, these notices could produce an impossible burden for service providers, who would be faced with ceaseless choices of suppressing controversial speech or sustaining prohibitive liability.

“Section 230 is a sword and shield,” said Sen. Wyden in a speech on the Senate floor in March. “It offers protection for liability, but it also gives companies the power — and the responsibility — to foster the sort of internet Americans want to be part of.”

Congress has made one successful attempt to chip away at Section 230, and there’s a growing appetite for regulating the internet and tech. A recent poll from the market research firm Harris X found that 84 percent of Americans think tech companies should be legally responsible for the content they carry, and 83 percent think there should be tougher regulations. They might not realize what that means giving up.