President Trump is preparing to sign an executive order Thursday that could roll back the immunity that tech giants have for the content on their sites, according to two people familiar with the matter.

Trump’s directive chiefly seeks to embolden federal regulators to rethink a portion of law known as Section 230, according to the two people, who spoke on the condition of anonymity to describe a document that could still evolve and has not been officially signed by the president. That law spares tech companies from being held liable for the comments, videos and other content posted by users on their platforms.

The law is controversial. It allows tech companies the freedom to police their platforms for abuse without fear of lawsuits. But critics say those exceptions have also allowed some of Silicon Valley’s most profitable companies to skirt responsibility for the harmful content that flourishes on their online platforms, including hate speech, terrorist propaganda and election-related falsehoods.

The order would prompt federal officials to open a proceeding to reconsider the scope of the law, the people familiar with the document said. A change could mean potentially dramatic free-speech implications and wide-ranging consequences for a broad swath of companies reliant on doing business on the Internet.

The order would also seek to channel complaints about political bias to the Federal Trade Commission, which would be encouraged to probe whether tech companies’ content-moderation policies are in keeping with their pledges of neutrality. It would also require federal agencies to review their spending on social media advertising, according to the people familiar with the White House’s thinking.

“In a country that has long cherished the freedom of expression, we cannot allow a limited number of online platforms to hand-pick the speech that Americans may access and convey online,” according to an undated draft version of the executive order obtained by The Washington Post late Wednesday.

The wide-ranging order comes two days after Twitter took the rare step of labeling one of the president’s tweets and linking viewers to news articles that fact-checked his claims. The move infuriated Trump and his supporters, who quickly blasted Twitter and its peers in Silicon Valley for engaging in censorship and exhibiting political bias. The companies have long denied those charges.

The executive order has gone through multiple iterations in recent years, and it may still change, the people said. The order would task the Commerce Department with petitioning the Federal Communications Commission to open a proceeding on Section 230.

Even so, it would be up to the FCC and the FTC, two independent agencies operating outside the president’s Cabinet, to determine exact courses of action once Trump signs it.

The order will mark the White House’s most significant salvo against Silicon Valley after years of verbal broadsides and regulatory threats from Trump and his top deputies. It also may raise fresh, thorny questions about the First Amendment, the future of expression online and the extent to which the White House can properly — and legally — influence the decisions that private companies make about their apps, sites and services.

The White House declined to comment. A White House spokesperson told reporters earlier Wednesday that the president would sign an executive order “pertaining to social media” on Thursday but did not provide further details.

Trump later in the evening again charged that the tech industry sought to “censor” conservatives in the approach to the 2020 election.

The FCC and the FTC did not immediately respond to requests for comment. Facebook did not have immediate comment. Twitter declined to comment, as did YouTube, which is part of Google-owner Alphabet.

Trump is one of social media’s most prolific, influential users. He’s armed with a Twitter account that reaches more than 80 million people and a campaign war chest that has made the president one of the most pervasive advertisers on Facebook and Google. But he is also one of the Web’s most controversial voices. He has previously shared and tweeted posts, photos and videos that appear to run afoul of major tech companies’ guidelines that prohibit or discourage harmful, abusive or false content.

For years, Twitter in particular largely allowed Trump to share his views unfettered anyway, saying that even his most controversial tweets were in the public interest. Fierce blowback eventually forced Twitter to reconsider its hands-off approach, culminating in the company’s first-ever attempt Tuesday to label the president’s tweets about mail-in ballots.

Trump responded by claiming that major social media companies are biased, threatening to “strongly regulate, or close them down” in response.

Until this week, Trump had issued only threats to regulate or penalize Facebook, Google-owned YouTube and Twitter over a range of claims, even suggesting at one point that the industry tried to undermine his election. Previously, however, the White House has backed down, even shelving prior versions of its executive order targeting social media companies.

In July, the president convened a “social media summit” at the White House featuring GOP lawmakers and Republican strategists, an event seen at the time as a precursor for further action to come. The event drew sharp rebukes from digital experts and congressional Democrats, who said Trump had used the backdrop of the White House to condone some of his supporters’ most provocative, controversial online tactics.

That same month, the Justice Department opened a wide-ranging review of the tech industry, which since has blossomed into a full inquiry on Section 230. Repeatedly, Attorney General William P. Barr has raised the possibility that the U.S. government could seek changes to the rules. “No longer are tech companies the underdog upstarts,” Barr said in a speech this February, reflecting on the origin of the statute. “They have become titans.”

Republican lawmakers also say that Facebook, Google and Twitter should be held accountable for perceived political bias, a call echoed by White House officials.

Meanwhile, in the wake of the fact-check label applied to Trump’s tweet, Twitter CEO Jack Dorsey and Facebook CEO Mark Zuckerberg engaged in a public battle over censoring content late Wednesday.

Zuckerberg appeared on Fox News, saying that he didn’t believe digital platforms should act as the “arbiter of truth of everything that people say online.”

Later that night, Dorsey lashed back at Zuckerberg in a series of tweets, saying that Twitter would continue would to point out incorrect or disputed information about elections globally.

But, he added, “This does not make us an ‘arbiter of truth.’ ”

Elizabeth Dwoskin contributed to this report.