While most Americans enjoy eating meat, it is hard to stomach the often sadistic treatment of factory-farmed cows, pigs and chickens. Farm operators know this, and they go to great lengths to hide these gruesome images from the public. A popular tactic pushed lately by the agriculture lobby is the so-called ag-gag law , which makes it a crime to secretly videotape industrial feedlots and slaughterhouses for the purpose of exposing animal mistreatment and abuse. These laws, on the books in seven states, purport to be about the protection of private property, but they are nothing more than government-sanctioned censorship of a matter of public interest. On Aug. 3, a federal judge struck down Idaho’s ag-gag law for violating the First Amendment — the first time a court has ruled on such a statute. Idaho lawmakers passed the bill last year in response to the release of undercover videos taken by Mercy for Animals , an animal-welfare group, at local factory farms...