Law professor David Kaye tweeted this recently: “Homework assignment: draft the rule that prohibits doctored Pelosi video but protects satire, political speech, humor etc. not so easy is it?” Kaye’s tweet came amid a flurry of calls for Facebook to take down an altered video of House Speaker Nancy Pelosi. As the UN’s special rapporteur on freedom of expression, Kaye has been working on this homework assignment for years, reporting on how governments and private companies should moderate social platforms. His new book “Speech Police” explores how transparency and democratic oversight of regulations on speech can help curb harmful content on the internet while protecting free expression.