https://arstechnica.com/tech-policy/2018/05/judge-orders-donald-trump-to-stop-blocking-people-on-twitter/

A federal judge ruled on Wednesday that Donald Trump's use of the Twitter block button violated the First Amendment. The ruling has implications for any government official—federal, state, or local—who uses Twitter or other social media platforms to communicate with the public.

The block button is a key weapon in Twitter's war against trolling and harassment, and Trump has used it since long before he was president. But last year, a group of Twitter users who had been blocked by Trump's @realDonaldTrump account sued, arguing that the use of the feature by a public official violates the First Amendment.