International law applies to outer space. Such law includes the United Nations (UN) Charter, which requires all UN members to settle disputes by peaceful means, prohibits the threat to use or actual use of force against the territorial integrity or political independence of another state, and recognizes a state's inherent right to act in individual or collective self-defense.
Outer space, the Moon, and other celestial bodies are not subject to appropriation by claim of sovereignty, use or occupation, or any other means. In 1976 eight equatorial countries claimed sovereignty over the geostationary orbital arc above their territory. Most other countries, including all major space powers, rejected the claim.
Outer space is free for use by all countries. This principle is related to the nonappropriation principle and is analogous to the right of innocent passage on the high seas.
Outer space will be used for peaceful purposes only. Most Western nations, including the US, equate peaceful purposes with nonaggressive ones. Consequently, all nonaggressive military use of space is permitted, except for certain activities, noted elsewhere in this section, that are specifically prohibited.
Objects launched into space must be registered with the UN.
A country retains jurisdiction and control over its registered space objects. This rule applies regardless of the condition of the objects.
A country is responsible for regulating, and is ultimately liable for, the outer space activities of its citizens.
Nuclear weapons tests and other nuclear explosions in outer space are prohibited. In 1958, before this prohibition, the US exploded three small nuclear devices in outer space over the course of two weeks in Project Argus. Such an experiment would be prohibited today.
Nuclear weapons and other weapons of mass destruction (such as chemical and biological weapons) may not be placed into orbit, installed on celestial bodies, or stationed in space in any other manner.
A country may not test any kind of weapon; establish military bases, installations, or fortifications; or conduct military maneuvers on celestial bodies. The use of military personnel for scientific research or other peaceful purposes is permitted.
The development, testing, or deployment of space-based antiballistic missile (ABM) systems or components is prohibited. This prohibition does not apply to research and development of space-based ABMs preceding field testing. This provision of the ABM Treaty and, in fact, the entire treaty (see table 1) have received much public attention in recent years because of progress in the Strategic Defense Initiative. It is quite possible that signatories could renegotiate or even eliminate the treaty before the end of the decade.
Interfering with national technical means of verification is prohibited, provided such systems are operating in accordance with generally recognized principles of international law and are in fact being used to verify provisions of specific treaties.(4)
(Click Here for Table 1)
The US adheres to the premise in international law that any act not specifically prohibited is permitted. Thus, even though the list (see table 1) of prohibited acts is sizable, overall there are few legal restrictions on the use of space for nonaggressive military purposes. As a result, international law implicitly permits the performance of such traditional military functions as surveillance, reconnaissance, navigation, meteorology, and communications. It permits the deployment of military space stations; the testing and deployment in Earth orbit of nonnuclear, non-ABM weapon systems, including antisatellite weapons and space-to-ground conventional weapons; and the use of space for individual and collective self-defense as well as virtually any conceivable activity not specifically prohibited or otherwise constrained.
Another widely accepted premise is that treaties usually regulate activities between signatories only during peacetime. This rule holds true unless a treaty expressly states that its provisions apply or become operative during hostilities, or the signatories can deduce this from the nature of the treaty itself. In other words, countries presume that armed conflict will result in the suspension or termination of a treaty's provisions. Good examples are treaties whose purpose is to disarm or limit quantities of arms maintained by the signatories. Therefore, during hostilities, the scope of permissible military space activities may broaden significantly.
Finally, it is important to understand that historically the former Soviet Union has been the most important space power next to the US. Most of the space-related treaties to which the US has agreed were signed by the Soviet Union, and some are bilateral agreements exclusively with that nation. As the USSR dissolved, the US adopted a policy of continuing to observe the requirements of all treaties and to apply their provisions to the independent states that have emerged. Nevertheless, a degree of legal uncertainty is likely to exist for a period of years until precedent establishes policy more firmly or formal agreements are concluded with the new states. Although uncertainty applies on both sides, the obligations of the US under the new conditions are clear because the state of US sovereignty has not changed, and the spirit of the original agreements still exists for the most part. It is less clear that the emerging states of the former Soviet Union will feel obligated to observe past agreements, but there are indications at this writing that they will do so.