(Loic Venance/AFP/Getty Images)

TWENTY-SIX WORDS may be responsible for a system that today serves more than 4 billion people around the world. Now, some in Congress want to rewrite them.

Section 230 of the Communications Decency Act protects Internet companies from liability for posts from third parties, with few exceptions. It’s this immunity that allows sites such as Twitter to host hundreds of millions of people’s musings in real time and every consumer review service or website with a comments section to open itself up to conversation — all without fear of a flurry of lawsuits. (The Post, like all major news organizations, has occasionally cited Section 230 as a defense when appropriate in legal cases.)

To Sen. Josh Hawley (R-Mo.) and his compatriots in the conservative crusade against Silicon Valley’s so-called censorship, however, tech companies are not holding up their “end of the bargain.” Platforms, he says, hide behind a shield preventing them from being treated like publishers, while acting like publishers every time they stamp out hate speech or harassment. Mr. Hawley proposes a change: Regulators will certify sites as “politically neutral.” Those that pass muster can keep their protection, and those that do not can dress up for court.

But Section 230 was never supposed to be a bargain. In fact, the law exists to encourage companies to moderate content without worrying that exercising editorial discretion will get them treated as editors — to furnish them not only with a shield, but also with a sword. By casting content moderation as censorship, Mr. Hawley’s bill would push sites to discard systems crucial to making the Web a safer place. Twitter would probably have to look a lot more like Gab and Facebook a lot more like 4chan in order for them to earn the politically neutral designation. Otherwise, they’d lose their immunity and risk being sued into bankruptcy.

Still, Section 230 is not necessarily sacrosanct. The Gabs and 8chans of the Internet, where harassment is standard operating procedure and incitements to violence thrive, suggest that the statute may actually need an adjustment to promote the opposite end from Mr. Hawley’s: maintaining immunity for good Samaritans but stripping it from bad ones. One suggestion would require that companies take reasonable steps to guard against illegal behavior. Another would remove immunity only from companies that actively encourage or are primarily used for lawlessness — essentially, those whose entire business model is abuse.

These lines would be hard to draw, and there’s always the threat that Internet companies nervous about getting bogged down in expensive litigation would adopt overzealous removal policies. But if Congress is going to have any conversation about reforming Section 230, the aim should be sharpening companies’ sword, not dulling it. Otherwise, those 4 billion people will find the Internet a lot less friendly.