Four tobacco companies have filed a lawsuit seeking to block the U.S. government from forcing them to display new warning labels on cigarette packs. The labels use images including dead bodies and diseased lungs to warn of the dangers of smoking. In the suit, the companies say including the labels would violate their free speech rights and force them to “engage in anti-smoking advocacy” on the government’s behalf. The labels would mark the first change to U.S. cigarette warnings in 25 years.