United States. According to the Congressional Research Service, as of 2009[update] there were roughly twice as many guns per capita in the United States as there were in 1968: more than 300 million guns in all.[4][5] The vast majority of unregistered firearms in the U.S. are lawfully unregistered; a Federal registry is prohibited by law, and only nine states impose registration requirements upon some or all firearms. See Gun laws in the United States by state for specific details.