World War I, given all the rousing “Over-There” songs and in-the-trenches films it inspired, was, at its outset, surprisingly unpopular with the American public. As opposition increased, Woodrow Wilson’s presidential administration became intent on stifling antiwar dissent. In his absorbing new book, Eric Chester reveals that out of this turmoil came a heated public discussion on the theory of civil liberties—the basic freedoms that are, theoretically, untouchable by any of the three branches of the U.S. government. The famous “clear and present danger” argument of Supreme Court...