James, it's a regulation under ITAR, international trade for those under the United States Munitions List. And, according to US State Department site:

"Who Must Register

All manufacturers, exporters, and brokers of defense articles, related technical data and defense services as defined on the United States Munitions List (Part 121 of the ITAR) (PDF, 7MB) are required to register with the Directorate of Defense Trade Controls (DDTC). Registration is primarily a means to provide the U.S. Government with necessary information on who is involved in certain manufacturing, exporting and brokering activities. Registration does not confer any export rights or privileges, but is a precondition for the issuance of any license or other approval for export."