Satellite explorations of the near earth environment have vastly increased our understanding of space plasmas and their interactions with systems. A logical next step involves active experiments in which small quantities of matter and energy are injected into space environments. These experiments seek to verify tentative, scientific understanding and to identify ways to control environmental effects on systems. Serious questions may be raised regarding the legitimacy of conducting active experiments in space under United States military auspices. Here we review the treaty obligations regarding space environment modification to which the United States government has committed itself. Experiments involving the detonation of nuclear devices or interference with foreign space assets, especially "national technical means of verification", are explicitly forbidden. In planned these experiments great care must be exerted so that they produce no" widespread, long-lasting or severe effects" on the environment. We also review active experiments programs conducted by U.S. civilian and foreign space agencies. Finally, the treaty restrictions are applied to the case of a hypothetical experiment to establish the feasibility of controlling the flux of energetic particles trapped in the earth's radiation belts. An ability to reduce trapped radiation would increase orbit selection options for future space-based surveillance systems.