A federal appeals court has reinstated a free speech lawsuit brought on behalf of a Colorado high school student who was expelled after posting a joking reference to exterminating Jews in his Snapchat messages. The appeals court said the U.S. Supreme Court’s decision last year, in a case involving a cheerleader’s vulgar messages on social media, that schools may not, in most circumstances, discipline off-campus student speech led to the conclusion that the Colorado student’s Snapchat message was likely protected under the First Amendment. The three-judge panel of the U.S. Court of Appeals for the 10th Circuit, in Denver, unanimously...