Columbia University’s Knight First Amendment Institute is suing Donald Trump for blocking people on Twitter, claiming that it violates free speech protections. The institute filed suit today on behalf of seven Twitter users who were blocked by the president, which prevents them from seeing or replying to his tweets. It threatened legal action in a letter to Trump in June, and now “asks the court to declare that the viewpoint-based blocking of people from the @realDonaldTrump account is unconstitutional.” The lawsuit, which was filed in the Southern District of New York, elaborates on the Knight Institute’s earlier letter. It contends...