Sometimes we wonder if we’re still living in the land of the free. Witness the subpoena from Claude Walker, attorney general of the U.S. Virgin Islands, demanding that the Competitive Enterprise Institute cough up a decade of emails and policy work, as well as a list of private donors. Mr. Walker is frustrated that the free-market think tank won’t join the modern church of climatology, so he has joined the rapidly expanding club of Democratic politicians and prosecutors harassing dissenters. New York Attorney General Eric Schneiderman started the assault last autumn with a subpoena barrage on Exxon Mobil. His demand...