It’s an unlikely way to begin a legal debate that may point the way toward global free speech rights on the Internet. But a British athlete’s sexual affair has triggered it, and caught in the middle is the pithy social website Twitter and its general counsel, Alexander Macgillivray, who’s been busy tweeting about user rights.

The dispute started in secret, when a U.K. soccer star obtained a so-called “super injunction,” preventing the British media from naming him as the person who had an affair with a reality-TV contestant.