Some call it the foundation of the open internet and online free speech. Others say it allows big platforms to avoid responsibility for harmful content they host.
Section 230 -- which the White House is seeking to curtail as part of its war with Silicon Valley -- was included in the 1996 Communications Decency Act to protect online service providers from lawsuits based on user-generated content.
It reads: "No provider or user of an interactive computer service shall be treated as the publisher or speaker of any information provided by another information content provider."
The passage is hailed in a 2019 book "The Twenty-Six Words That Created the Internet" by law professor Jeff Kosseff as the basis for the flourishing online economy and services such as Facebook, YouTube, Twitter and Wikipedia, among others.
"Without Section 230, these companies could be sued for their users' blog posts, social media ramblings or homemade online videos."
Kosseff acknowledges that the freewheeling online ecosystem enabled by Section 230 has "significant social costs" and that it "enables terrorist recruitment, online sex trafficking, discriminatory housing sales and vicious harassment."
But he concludes that despite the drawbacks it has fostered "innovation and freedom" and delivers a "net benefit" to society.
The legal immunity Section 230 provides has been attacked by President Donald Trump -- especially after Twitter labeled two of his posts this week as misleading -- along with other politicians from the left and right.
Republican Senator Josh Hawley said earlier this year that the law gives tech companies "a sweetheart deal that no other industry enjoys: complete exemption from traditional publisher liability."
Democratic presidential candidate Joe Biden said in January Section 230 should be "revoked" in the case of Facebook, which was "propagating falsehoods."
According to a draft, the White House order states that "we cannot allow a limited number of online platforms to hand-pick the speech that Americans may access and convey online. This practice is fundamentally un-American and anti-democratic."
It states that by restricting certain content, the online services are "engaged in editorial conduct" and as a result should lose any protection from liability.
Defenders of the law say critics miss the point, that it protects online operators large and small, not just big tech platforms, from content hosted online but produced by users.
"Section 230 protects the comments section on a retiree's baking blog as much as it protects Facebook," says Matthew Feeny of the libertarian Cato Institute.
Section 230 effectively implements the US constitution's First Amendment guarantees of free speech with some procedural streamlining to avoid a wave of litigation, according to legal experts.
Some say Trump and others are distorting the First Amendment, which was designed to prevent government interference with private expression, as well as Section 230.
"The First Amendment protects Twitter from Trump -- not Trump from Twitter," says Ashkhen Kazaryan of the think tank Tech Freedom.
Law professors Laurence Tribe and Joshua Geltzer, writing in The Washington Post, say that by seeking to regulate content online, "Trump is already committing the very violation of which he's accusing Twitter."
They write that Section 230 "was passed precisely to provide social media companies with the flexibility to regulate content on their platforms responsibly, even as they played a very different role from that of traditional publishers because social media companies don't scrutinize content before it is uploaded to their platforms."