Federal Prohibitions on Certain Types of Firearms

A partial list of Federally banned firearms include short barreled rifles, short barreled shotguns, full automatic firearms more commonly known as machine guns (including bump stocks), firearms that are not detectable by metal detectors, and firearms without serial numbers or that have the serial number or other identification required by this chapter obliterated, removed, changed or altered.

18 U.S. Code § 922(o) Unlawful acts

(1) Except as provided in paragraph (2), it shall be unlawful for any person to transfer or possess a machine gun.
(2) This subsection does not apply with respect to

(A) a transfer to or by, or possession by or under the authority of, the United States or any department or agency thereof or a State, or a department, agency or political subdivision thereof; or
(B) any lawful transfer or lawful possession of a machinegun that was lawfully possessed before the date this subsection takes effect.

(p)

(1) It shall be unlawful for any person to manufacture, import, sell, ship, deliver, possess, transfer or receive any firearm

(A) that, after removal of grips, stocks and magazines, is not as detectable as the Security Exemplar, by walk-through metal detectors calibrated and operated to detect the Security Exemplar; or
(B) any major component of which, when subjected to inspection by the types of x-ray machines commonly used at airports, does not generate an image that accurately depicts the shape of the component. Barium sulfate or other compounds may be used in the fabrication of the component.

(2) For purposes of this subsection—

(A) the term “firearm” does not include the frame or receiver of any such weapon;
(B) the term “major component” means, with respect to a firearm, the barrel, the slide or cylinder, or the frame or receiver of the firearm; and
(C) the term “Security Exemplar” means an object, to be fabricated at the direction of the Attorney General, that is—

(i) constructed of, during the 12-month period beginning on the date of the enactment of this subsection, 3.7 ounces of material type 17–4 PH stainless steel in a shape resembling a handgun; and
(ii) suitable for testing and calibrating metal detectors:
Provided, however, that at the close of such 12-month period, and at appropriate times thereafter, the attorney general shall promulgate regulations to permit the manufacture, importation, sale, shipment, delivery, possession, transfer or receipt of firearms previously prohibited under this subparagraph that are as detectable as a “Security Exemplar” which contains 3.7 ounces of material type 17–4 PH stainless steel, in a shape resembling a handgun, or such lesser amount as is detectable in view of advances in state-of-the-art developments in weapons detection technology.

(3) Under such rules and regulations as the attorney general shall prescribe, this subsection shall not apply to the manufacture, possession, transfer, receipt, shipment or delivery of a firearm by a licensed manufacturer or any person acting pursuant to a contract with a licensed manufacturer, for the purpose of examining and testing such firearm to determine whether paragraph (1) applies to such firearm. The attorney general shall ensure that rules and regulations adopted pursuant to this paragraph do not impair the manufacture of prototype firearms or the development of new technology.
(4) The attorney general shall permit the conditional importation of a firearm by a licensed importer or licensed manufacturer, for examination and testing to determine whether or not the unconditional importation of such firearm would violate this subsection.
(5) This subsection shall not apply to any firearm which—

(A) has been certified by the Secretary of Defense or the Director of Central Intelligence, after consultation with the attorney general and the administrator of the Federal Aviation Administration, as necessary for military or intelligence applications; and
(B) is manufactured for and sold exclusively to military or intelligence agencies of the United States.

(6) This subsection shall not apply with respect to any firearm manufactured in, imported into or possessed in the United States before the date of the enactment of the Undetectable Firearms Act of 1988.

26 U.S.C. § 5861. Prohibited acts

It shall be unlawful for any person–

(a)  to engage in business as a manufacturer or importer of, or dealer in, firearms without having paid the special (occupational) tax required by section 5801 for his business or having registered as required by section 5802 ;
(b)  to receive or possess a firearm transferred to him in violation of the provisions of this chapter;
(c)  to receive or possess a firearm made in violation of the provisions of this chapter;
(d)  to receive or possess a firearm which is not registered to him in the National Firearms Registration and Transfer Record;
(e)  to transfer a firearm in violation of the provisions of this chapter;
(f)  to make a firearm in violation of the provisions of this chapter;
(g)  to obliterate, remove, change or alter the serial number or other identification of a firearm required by this chapter;
(h)  to receive or possess a firearm having the serial number or other identification required by this chapter obliterated, removed, changed or altered;
(i)  to receive or possess a firearm which is not identified by a serial number as required by this chapter;
(j)  to transport, deliver or receive any firearm in interstate commerce which has not been registered as required by this chapter;
(k)  to receive or possess a firearm which has been imported or brought into the United States in violation of section 5844; or
(l)  to make, or cause the making of, a false entry on any application, return or record required by this chapter, knowing such entry to be false.

27 Code of Federal Regulations Parts 447, 478, and 479

As of  March 26, 2019 the definition of machine gun includes bumpstock-type devices—meaning ‘‘bump fire’’ stocks, slide-fire devices, and devices with certain similar characteristics—are ‘‘machine guns’’ as defined by the National Firearms Act of 1934 and the Gun Control Act of 1968 because such devices allow a shooter of a semiautomatic firearm to initiate a continuous firing cycle with a single pull of the trigger. Specifically, these devices convert an otherwise semiautomatic firearm into a machine gun by functioning as a self-acting or self-regulating mechanism that harnesses the recoil energy of the semiautomatic firearm in a manner that allows the trigger to reset and continue firing without additional physical manipulation of the trigger by the shooter. Hence, a semiautomatic firearm to which a bump-stock-type device is attached is able to produce automatic fire with a single pull of the trigger. With limited exceptions, the Gun Control Act, as amended, makes it unlawful for any person to transfer or possess a machine gun unless it was lawfully possessed prior to the effective date of the statute. The bump-stock-type devices covered by this final rule were not in existence prior to the effective date of the statute, and therefore were prohibited when this rule became effective. Consequently, under the final rule, current possessors of these devices were required to destroy the devices or abandon them at an ATF office prior to the effective date of the rule.