International Legal Agreements Relevant to Space Weapons

Published Feb 11, 2004

Nuclear space satellite.

The military utility of space has long been recognized and exploited. In fact, the reconnaissance, navigation, and communications functions of space assets are critical to war-making and peacekeeping missions of the US military. However, states have so far resisted positioning destructive weapons in space or intentionally destroying the space assets of other states. Recent policy and planning documents of the United States suggest that strategic control of space is a priority of the current administration and that anti-satellite weapons are an important component of this plan. Also, the administration's national missile defense (NMD) agenda includes space-based NMD systems, which will likely be useful ASAT systems as well.

Strong and almost unanimous opposition to weaponization of space has been expressed in the United Nations Conference on Disarmament. China and Russia have drafted text for a treaty to ban space weapons. The United States, however, has refused to enter negotiations on such a treaty.

It is likely that the weaponization of space will begin in the foreseeable future unless it is hindered by organized, effective international opposition or the current US administration is replaced by an administration willing to cancel projects for weaponization of space in the face of considerable opposition from domestic proponents of weaponization.

Although no comprehensive treaty about space weapons is in effect, a legal framework does exist. To help frame this opposition, we review relevant international treaties that address aspects of the space weapons issue and discuss relevant United Nations resolutions.

The 1967 Outer Space Treaty

The Outer Space Treaty entered into effect in October 1967. It is the second "nonarmament" treaty (the first being the Antarctic Treaty of 1961). There is no expiration date. 

The first three articles of the treaty set general principles for the use of space; the rest of the articles are intended to guide the behavior of treaty parties.

Article I
The exploration and use of outer space, including the moon and other celestial bodies, shall be carried out for the benefit and in the interests of all countries, irrespective of their degree of economic or scientific development, and shall be the province of all mankind.

Outer space, including the moon and other celestial bodies, shall be free for exploration and use by all States without discrimination of any kind, on a basis of equality and in accordance with international law, and there shall be free access to all areas of celestial bodies.

There shall be freedom of scientific investigation in outer space, including the moon and other celestial bodies, and States shall facilitate and encourage international co-operation in such investigation.

Article II
Outer space, including the moon and other celestial bodies, is not subject to national appropriation by claim of sovereignty, by means of use or occupation, or by any other means.

Article III
States Parties to the Treaty shall carry on activities in the exploration and use of outer space, including the moon and other celestial bodies, in accordance with international law, including the Charter of the United Nations, in the interest of maintaining international peace and security and promoting international co-operation and understanding.

Article IV of the Outer Space Treaty prohibits placing in orbit around the earth any objects carrying nuclear weapons or any other kinds of weapons of mass destruction (WMD). It also prohibits the testing and the deployment of any kind of weapon on the moon or other celestial bodies.  

Article IV
States Parties to the Treaty undertake not to place in orbit around the earth any objects carrying nuclear weapons or any other kinds of weapons of mass destruction, install such weapons on celestial bodies, or station such weapons in outer space in any other manner.

The moon and other celestial bodies shall be used by all States Parties to the Treaty exclusively for peaceful purposes. The establishment of military bases, installations and fortifications, the testing of any type of weapons and the conduct of military manoeuvres on celestial bodies shall be forbidden. The use of military personnel for scientific research or for any other peaceful purposes shall not be prohibited. The use of any equipment or facility necessary for peaceful exploration of the moon and other celestial bodies shall also not be prohibited.

While Article IV bans WMD from orbit, it does not prohibit missile-borne WMD from transiting space or weapons other than WMD being placed in space orbit and used to attack targets in space or on Earth. There is no ban on air-, ground-, or conventional space-based anti-satellite or anti-missile weapons.

Article VI touches on the important point that States Parties to the Treaty are responsible for the national activities carried out by corporations and any other non-governmental agencies of that nation. In the context of the potential weaponization of space, Article VI provides a legal context within which actions may be challenged if they are perceived by other States Parties to the Treaty as non-peaceful uses of space.

Articles VII and IX also present possibilities for legal action in connection with space weaponization.

Article VII makes treaty parties that launch objects into outer space liable for damage to the property of another treaty party; the procedure is spelled out in the Liability Convention of 1972. The Liability Convention foresees the establishment of a Claims Commission to determine the extent of liability for damage by the space objects of one country to the space objects or property of another state.

Article IX of the Outer Space Treaty provides for consultations if any treaty party believes an activity planned by another treaty party would cause "potentially harmful interference with activities in the peaceful exploration and use of outer space."

Beyond this, the General Assembly could, by majority vote, request an advisory opinion from the International Court of Justice if either the peaceful-uses language or the extension of the UN Charter to space or these two articles on liability and consultation come into contention, for example, as the space-based component of the missile defense system advances.

In fact, requests for consultation or under Article IX—or also a General Assembly request for an advisory opinion—can come now in order to make world opinion aware of the weaponization issue before the damage has been done, and to make the US government more aware of the potential costs entailed in weaponizing space. 

The request for consultation under Article IX can come from any party or group of parties to the Outer Space Treaty. It has been noted that parties to the treaty could convene and issue an interpretation that US testing or orbiting of space weapons was contrary to the peaceful-uses language of the treaty, in effect amending the treaty to preclude weaponization.[1] The General Assembly could pass a resolution endorsing this interpretation.

Other space treaties

In addition to the 1967 Outer Space Treaty, five other treaties address space issues. These are: the  Limited Test Ban Treaty of 1963, which prohibits nuclear tests and any other nuclear explosions in the atmosphere or outer space; the Astronauts Rescue Agreement of 1968, requiring the safe return of astronauts and objects launched into space to their country of origin; the Liability Convention of 1972, establishing procedures for determining the liability of a state that damages or destroys space objects of another state; the Registration Convention of 1976 requiring the registration of objects launched into space; and the Moon Agreement of 1984, which took the first steps to establish a regime for exploiting the natural resources of space.[2] The latter four elaborate on aspects of the Outer Space Treaty.

Treaties Addressing Technical Means of Verification and Missile Defense

The concept of non-interference with national technical means of verification first appeared in the Strategic Arms Limitation Talks (SALT) I Treaty of 1972. It was taken over into the Intermediate Range Nuclear Forces (INF) Treaty, which is of indefinite duration, and into the Treaty on the Reduction and Limitation of Strategic Offensive Arms (START I), which has been extended to 2009. The intent of this noninterference measure is to preserve from attack or interference technical means of verifying treaty compliance, including space-orbiting means.

It would be a violation of the provisions on noninterference with national means of verification in the INF and START I treaties to use weapons against any early warning, imaging, or intelligence satellite and, by extension, against any ocean surveillance, signals, intelligence, or communications satellite of the United States or Russia. This obligation was made multilateral in the Conventional Forces in Europe (CFE) Treaty, which has 30 NATO and East European participants and is of unlimited duration.

Presumably, Russia, France, the European Union as such, or any other state party to the CFE Treaty could also take legal action against moves toward space weaponization, basing its complaint on treaty provisions prohibiting interference with national technical means of verification. Legal action could also be taken in US courts by foreign or US commercial users of space satellites if these satellites were endangered or destroyed by US space weapons.

The Anti-Ballistic Missile (ABM) Treaty temporarily provided a prohibition against the testing or deploying of weapons in space (other than weapons of mass destruction). The US withdrawal from the ABM Treaty became effective on June 13, 2002, rendering the prohibition null.

UN resolutions

The UN General Assembly has passed resolutions each year for the past 22 years calling for the continued peaceful use of space and the prevention of an arms race in space. The resolution asks all states to refrain from actions contrary to the peaceful use of outer space and calls for negotiation in the Conference on Disarmament on a multilateral agreement to prevent an arms race in outer space. Most of these resolutions have been unanimous and without opposition, although the United States and a few other governments have abstained. In the most recent version, adopted by the First Committee of the General Assembly in November 2002, there were 151 votes for the resolution with zero opposed. The US and Israel abstained, and 38 permanent representatives were absent from the First Committee.

These repeated, nearly unanimous resolutions—against which the United States does not find it expedient to vote—not only demonstrate the existence of a norm against the weaponization of space. They also indicate a widespread desire to expand existing multilateral agreements to include an explicit prohibition against all weapons in space.

Beyond this, there are five relevant General Assembly resolutions. They are: the Declaration of Legal Principles Governing the Activities of States in the Exploration and Uses of Outer Space (1963), which preceded the Outer Space Treaty and laid out most of its content; the Declaration on International Cooperation in the Exploration and Use of Outer Space for the Use and Benefit and in the Interest of All States (1996); and resolutions on Direct Television Broadcasting, Remote Sensing of the Earth from Outer Space (which seeks to ensure affordable access by developing countries to non-military satellite imaging), and the Use of Nuclear Power in Outer Space (which deals with limiting exposure in the crash landing of nuclear-powered satellites and the liability for such accidents).3 

Other international instruments are pertinent to space. The International Telecommunication Union (ITU) allocates radio frequencies used by satellites. It would be difficult for any one country to operate satellites without coordinating their efforts through the ITU. This encourages state cooperation and also provides a locus of influence should the United States or another state pursue behaviors, such as the deployment of space weapons, that are dangerous for other states.

Expansion of the legal regime

There have been many proposals to fill the gap in the Outer Space Treaty's prohibition of weapons. Canada and many NGOs have made proposals. The most recent suggestion is a Russia-China working paper presented to the UN Conference on Disarmament (CD) on June 27, 2002, which contains possible elements of an international legal agreement on prohibiting the deployment of any weapons in outer space. It would also prohibit the threat or use of force against space objects, a concept that would ban anti-satellite weapons, either mounted on aircraft or ground-based.

At present, there is no prospect that this treaty outline will make progress at the CD, owing to the conference rule of consensus decisions and the outright opposition of the United States.

The United States has said it is willing to discuss this issue at the CD, but not to negotiate a treaty on it. China had long insisted that, in addition to discussion, the possibility of negotiation must be mentioned in the agenda, however in August, 2003, China signaled it was prepared to compromise on this point.4 There is even some agitation to change the consensus rules of the Conference on Disarmament. In the meantime, the Russian-Chinese draft can be refined further and developed into a usable treaty text, with help from other governments and NGOs.

Repercussions from violating space law, such as lawsuits and international legal actions, should be included in the calculation of gains and losses from weaponization.


  1. George Bunn and John Rhinelander, June 2002 letter to the editor in Arms Control Today : see
  2. The Agreement on the Rescue of Astronauts, the Return of Astronauts and the Return of Objects Launched into Outer Space (the "Rescue Agreement"), opened for signature on 22 April 1968, entered into force on 3 December 1968, 87 ratifications; The Convention on International Liability for Damage Caused by Space Objects (the "Liability Convention"), opened for signature on 29 March 1972, entered into force on 1 September 1972, 81 ratifications; The Convention on Registration of Objects Launched into Outer Space (the "Registration Convention") opened for signature on 14 January 1975, entered into force on 15 September 1976, 43 ratifications); The Agreement Governing the Activities of States on the Moon and Other Celestial Bodies (the "Moon Agreement"), opened for signature on 18 December 1979, entered into force on 11 July 1984, 9 ratifications (As of 1 February 2001).
  3. The Declaration of Legal Principles Governing the Activities of States in the Exploration and Uses of Outer Space (General Assembly resolution 1962 (XVIII) of 13 December 1963); The Principles Governing the Use by States of Artificial Earth Satellites for International Direct Television Broadcasting (resolution 37/92 of 10 December 1982); The Principles Relating to Remote Sensing of the Earth from Outer Space (resolution 41/65 of 3 December 1986); The Principles Relevant to the Use of Nuclear Power Sources in Outer Space (resolution 47/68 of 14 December 1992); The Declaration on International Cooperation in the Exploration and Use of Outer Space for the Benefit and in the Interest of All States, Taking into Particular Account the Needs of Developing Countries (resolution 51/122 of 13 December 1996).

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