President Donald Trump signed an executive order targeting social media companies on Thursday, days after Twitter flagged two of the president’s tweets as “potentially misleading” for the first time.

The order was designed to “defend free speech from one of the gravest dangers it has faced in American history,” Trump said.

“A small handful of social media monopolies controls a vast portion of all public and private communications in the United States,” he said at the Oval Office on Thursday. “They’ve had unchecked power to censor, restrict, edit, shape, hide, alter, virtually any form of communication between private citizens and large public audiences.”

It is unclear how enforceable the law would be, as some experts argue that it borders on an infringement of the First Amendment rights of private companies.

“I guess it’s going to be challenged in court, what isn’t?” Trump noted on Thursday. “But I think we’re going to do very well.”

The order attempts to reinterpret Section 230 of the Communications Decency Act. from 1996 which largely protects websites from lawsuits.

“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 on the internet,” the order reads. “This practice is fundamentally un-American and anti-democratic. When large, powerful social media companies censor opinions with which they disagree, they exercise a dangerous power.”

Twitter called Trump’s order “is a reactionary and politicized approach to a landmark law.”

“#Section230 protects American innovation and freedom of expression, and it’s underpinned by democratic values,” the company tweeted. “Attempts to unilaterally erode it threaten the future of online speech and Internet freedoms.”