In the United States, pen guns that can fire bullet or shot cartridges and do not require a reconfiguration to fire (e.g., folding to the shape of a pistol) are federally regulated as an Any Other Weapon (Title II). They require registration under the National Firearms Act and a tax in the amount of five dollars is levied.[7][8]
According to the FBI, pen guns were widely used for self-defense in the 20th century.[9]
^Stephen D. Carpenteri (October 2013). Gun Trader's Guide, Thirty-Fifth Edition: A Comprehensive, Fully Illustrated Guide to Modern Firearms with Current Market Values. Skyhorse Publishing. ISBN978-1626360259.