International Traffic in Arms Regulations (ITAR) control the export and import of defense-related articles and services on the United States Munitions List (USML). According to the U.S. Government, all manufacturers, exporters, and brokers of defense articles, defense services, or related technical data must be ITAR compliant. Therefore, more companies are requiring their supply chain members to be ITAR compliant as well. In General:

For a company involved in the manufacture, sale or distribution of goods or services covered under the USML, or a component supplier to goods covered under the United States Munitions List (USML), the stipulation or requirement of being “ITAR certified (compliant)” means that the company must be registered with the State Department’s Directorate of Defense Trade Controls (DDTC) if required as spelled out on DDTC’s website and the company must understand and abide by the ITAR as it applies to their USML linked goods or services. The company themselves are certifying that they operate in accordance with the ITAR when they accept being a supplier for the USML prime exporter.

In other words, companies must register with the DDTC and know what is required of them to be ITAR compliant and then certify that they possess that knowledge.