Nathan Haddad, a former Army staff sergeant in New York, was selling his gun magazines when he was arrested for violating a state law prohibiting possession of magazines that hold more than 10 rounds. He was arrested and charged with five felonies. This is the crime that David Gregory of NBC News committed in Washington a few months ago; Mr. Gregory was not prosecuted because he’s, umm, well, a celebrity. The district attorney for Jefferson County, N.Y., offered Sgt. Haddad, now a civilian employee at Fort Drum, N.Y., a deal that would require him to plead guilty to five Class...