International Traffic in Arms Regulation

International Traffic in Arms Regulations (ITAR) is a United States regulatory regime to restrict and control the export of defense and military related technologies to safeguard U.S. national security and further U.S. foreign policy objectives.

Defense-related articles and services on the United States Munitions List (USML) are covered by the regulations, which implement the provisions of the Arms Export Control Act (AECA), and are described in Title 22 (Foreign Relations), Chapter I (Department of State), Subchapter M of the Code of Federal Regulations. The Department of State Directorate of Defense Trade Controls (DDTC) interprets and enforces ITAR. The related Export Administration Regulations (Code of Federal Regulations Title 15 chapter VII, subchapter C) are enforced and interpreted by the Bureau of Industry and Security in the Commerce Department. The Department of Defense is also involved in the review and approval process. Physical enforcement of the ITAR; and all import and export laws of the United States is performed by Homeland Security Investigations Special Agents (formerly U.S. Customs) under Immigration and Customs Enforcement, an agency of the Department of Homeland Security. Additionally, Customs and Border Protection Officers, also under the Department of Homeland Security, inspect imports and exports at U.S. Border Crossings and International Airports and enforce import and export regulations.

For practical purposes, ITAR regulations dictate that information and material pertaining to defense and military related technologies (items listed on the U.S. Munitions List) may only be shared with U.S. Persons unless authorization from the Department of State is received or a special exemption is used. U.S. Persons (including organizations) can face heavy fines if they have, without authorization or the use of an exemption, provided foreign persons with access to ITAR-protected defense articles, services or technical data.

...
Wikipedia