Undetectable Firearms Act of 1988

Terrorist Firearms Detection Act of 1988 - Amends the Federal criminal code to prohibit the manufacture, importation, sale, transfer, or possession of plastic firearms. Defines the term "plastic firearm" to mean any firearm: (1) containing less than 3.7 ounces of metal; or (2) of which any major component, when subjected to inspection by x-ray machines commonly used at airports, does not generate an image that accurately depicts the shape of the component. States that no provision of this Act shall apply to conduct by or under the authority of the Federal or State governments. Provides an exemption from such prohibition for any firearm possessed in the United States before the enactment of this Act. Requires the Secretary of the Treasury to submit biennial reports to the Congress regarding the state of the art of firearm manufacture and firearm detection technology. Repeals such prohibition five years after the effective date of this Act.