Order Signed Link to draft Executive Order (PDF): Washington (CNN)President Donald Trump signed an executive order targeting social media companies on Thursday, days after Twitter called two of his tweets "potentially misleading." Speaking from the Oval Office ahead of signing the order, Trump said the move was to "defend free speech from one of the gravest dangers it has faced in American history." "A small handful of social media monopolies controls a vast portion of all public and private communications in the United States," he claimed. "They've had unchecked power to censor, restrict, edit, shape, hide, alter, virtually any form of communication between private citizens and large public audiences." The executive order tests the boundaries of the White House's authority. In a long-shot legal bid, it seeks to curtail the power of large social media platforms by reinterpreting a critical 1996 law that shields websites and tech companies from lawsuits. But legal experts on both the right and the left have raised serious concerns about the proposal. They say it may be unconstitutional because it risks infringing on the First Amendment rights of private companies and because it attempts to circumvent the two other branches of government. "(Trump) is trying to steal for himself the power of the courts and Congress to rewrite decades of settled law," said Democratic Sen. Ron Wyden of Oregon, the architect of the legislation that the order seeks to reinterpret. "He decides what's legal based on what's in his interest." The order marks a dramatic escalation by Trump in his war with tech companies as they struggle with the growing problem of misinformation on social media. The President has regularly accused sites of censoring conservative speech. On Thursday, Trump acknowledged that legal challenges to the order are on the horizon, saying he was "sure they'll be doing a lawsuit." "I guess it's going to be challenged in court, what isn't?" he asked. "But I think we're going to do very well." A draft of the order, which was reviewed by CNN, targets a law known as the Communications Decency Act. Section 230 of the legislation provides broad immunity to websites that curate and moderate their own platforms, and has been described by legal experts as "the 26 words that created the internet." It argues that the protections hinge mainly on tech platforms operating in "good faith," and that social media companies have not. "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," the draft order says. "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." On Tuesday, Twitter applied a fact-check to two of Trump's tweets, including one that claimed, without evidence, that mail-in ballots would lead to widespread voter fraud. Trump immediately shot back, accusing the social media giant of censorship and warning that if it continued to offer addendums to his messages, he would use the power of the federal government to rein it in or even shut it down. The draft order also accuses social media platforms of "invoking inconsistent, irrational, and groundless justifications to censor or otherwise punish Americans' speech here at home." It also faults Google for helping the Chinese government surveil its citizens; Twitter for spreading Chinese propaganda; and Facebook for profiting from Chinese advertising. Facebook, Google and Twitter declined to comment.