Unlicensed 3D printing of guns is illegal and punishable by up to 10 years in prison, the government said on Thursday, as it moved to address growing public concern about plastic guns. Weapons made by printing their components are already banned under the 1968 Firearms Act, but the Home Office has updated its rules to prohibit the manufacture, sale, purchase and possession of them unless properly licensed. “The Liberator” handgun was invented by 25-year-old Cody Wilson, a Texan law student.