The Supreme Court has long held that, when the government establishes or operates a public forum like a town hall, the First Amendment bars the government from excluding disfavored voices or silencing disfavored views. The court treats such “viewpoint discrimination” as among the worst kinds of First Amendment violations.

Social media platforms like Twitter have come to play the role of digital-age public fora. They’re now a principal site of critical political debate and discussion. When a government officeholder or office uses a Twitter account for official government announcements—as Trump certainly has done—and opens that account for comments by and interaction with the public—as this president obviously has done—then that official and the office the official occupies create a modern-day town hall. Trump’s @realDonaldTrump Twitter account, like his less frequently used @POTUS account, is the site of many, perhaps most, of Trump’s initial announcements of major executive actions and newsworthy shifts in policy. That, in turn, means that the First Amendment forbids him from engaging in viewpoint discrimination in operating that forum.

Trump’s government attorneys essentially acknowledge that the president engaged in viewpoint discrimination by blocking critics on Twitter for comments that he disliked, but they argue that a private company like Twitter can’t be the site of a public forum. That’s ridiculous.