In Social-Media Era, When Is Free Speech Illegal?

A case before the Supreme Court over threats made on Facebook is highlighting long-standing tension between law enforcement and free-speech advocates over when threatening speech crosses a line and breaks the law.

The appeal, up for arguments on Dec. 1, presents a vexing legal issue courts have long struggled to settle, and it does so when what people say can reach a bigger audience than ever before through social media. Although social-media companies have rules for managing individual speech online, the outcome could affect the leeway people have to express themselves, even darkly and violently, on Facebook, Twitter, YouTube and other sites.