It has since helped social media firms escape legal judgment for a wide variety of things.
Last year the US court of appeals ruled that Facebook was not responsible for violence coordinated and incited by accounts linked to Palestinian Islamist militant group Hamas, citing the law.
Supporters of Section 230, including social media companies, argue that it actually enables the constitutional American right to free speech, because it means that technology companies can host legally dicey content without the fear of being held responsible.
Without the ability to moderate without fear of incurring legal penalty, they argue, the internet would either be a chaotic, abuse-filled, unworkable free-for-all or much more tightly regulated by companies who would fear the legal consequences of missing a legally problematic post.
The industry has rallied together to condemn the order, arguing that it will do far more harm than good.
Jon Berroya, head of the Internet Association, the trade union representing technology heavyweights like Google, Amazon, Facebook, pointed out that claims of bias “rely on isolated anecdotes that are undermined by the fact that politicians and political groups successfully use social media to reach millions of followers every day”.
He warned that revoking Section 230 would “undermine a variety of government efforts to protect public safety and spread critical information online”.
There’s also the argument that while large internet companies like Facebook and Twitter have the money and resources to defend themselves, any greater liability would be more onerous for smaller startups, potentially stifling competition in the industry.
Trump’s attack is only the latest in a series of changes which reduced the scope of the law. Backpage.com, a site which hosted many adverts for sexual services had repeatedly managed to defend itself from cases brought by trafficked women and girls and their families using section 230, until a law was brought in in 2018 to limit the immunity of sites which were “knowingly hosting third-party content that promotes or facilitates sex trafficking”.
In the US, politicians across the political spectrum have also criticised the law. Critiques from Democrats usually focus on harassment and content which is racist or otherwise offensive, with the argument that tech companies aren’t dedicated enough to removing it because of their immunity.
Right-wing politicians have argued that it empowers tech companies to stifle free speech by removing opinions that they don’t like.
It may have become the unofficial, and most regular, means of communication between the White House and the outside world, but Trump and Twitter have a chequered history.
Mr Trump’s latest attack on social media emerged after Twitter attached a warning to some of his tweets which prompted users to fact check his claims.
The tagged tweets included claims about postal voting, which have since been debunked. Mr Trump claimed that the mail-in ballots lead to vote fraud and ineligible voters getting ballots. Hours later he warned, on Twitter, that he would regulate social media companies, or “shut them down”.