The Knight First Amendment Institute at Columbia University warned President Trump to stop blocking Twitter users. The freedom of speech organization sent the president a letter last month arguing that when Twitter is used by a President, it operates as a "designated public forum" like a city council or school board meeting. When blocking users for mocking or critical tweets, it argues, the president is violating their First Amendment rights. While the letter did not explicitly promise legal action, the implication was clear. Now, the same institute has filed suit, asserting that President Trump and "his communications team are violating the First Amendment by blocking individuals from the @realDonaldTrump Twitter account because they criticized the president or his policies."