But the logic of Mr. Trump’s order is intriguing because it attacks the very legal provision that has allowed him such latitude to publish with impunity a whole host of inflammatory, harassing and factually distorted messages that a media provider might feel compelled to take down if it were forced into the role of a publisher that faced the risk of legal liability rather than a distributor that does not.

“Ironically, Donald Trump is a big beneficiary of Section 230,” said Kate Ruane, a senior legislative counsel for the American Civil Liberties Union, which instantly objected to the proposed order. “If platforms were not immune under the law, then they would not risk the legal liability that could come with hosting Donald Trump’s lies, defamation and threats.”

Mr. Trump has long posted false and disparaging messages to his 80 million followers on Twitter, disregarding complaints about their accuracy or fairness. In recent weeks, he has repeatedly issued tweets that essentially falsely accused Joe Scarborough, the MSNBC host, of murdering a staff member in 2001 when he was a congressman.