National Security Presidential Directive 39

Citation
The White House, National Security Presidential Directive 39 (NSPD 39): U.S. Space-Based Position, Navigation, and Timing Policy (Dec. 8, 2004) (full-text).

Overview
This policy provides guidance for: (1) development, acquisition, operation, sustainment, and modernization of the Global Positioning System and U.S.-developed, owned and/or operated systems used to augment or otherwise improve the Global Positioning System and/or other space-based positioning, navigation, and timing signals; (2) development, deployment, sustainment, and modernization of capabilities to protect U.S. and allied access to and use of the Global Positioning System for national, homeland, and economic security, and to deny adversaries access to any space-based positioning, navigation, and timing services; and (3) foreign access to the Global Positioning System and U.S. Government augmentations, and international cooperation with foreign space-based positioning, navigation, and timing services, including augmentations.