Unfortunately, the United States Supreme Court has fallen victim to the spurious reasoning that the National Rifle Association has spread about the Second Amendment. It invalidated the District of Columbia's gun control regulations. (See this site, though the post is in agreement with this stupid opinion.)
Though the opinion is stupid, it is the law of the land. Just as abortion opponents have to live with Roe v. Wade, we will have to live with District of Columbia v. Heller, the worst U. S. Supreme Court opinion since Plessy v. Ferguson. It means that it is going to be difficult to control gun violence, but of course there will be many further challenges to determine what can legally be done to control guns in this nation.