The Outer Space Treaty is the foundational international agreement governing military, civil, and commercial activities beyond Earth. Formally titled the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies, it was adopted by the United Nations General Assembly (UNGA) on December 19, 1966, opened for signature on January 27, 1967, and entered into force on October 10, 1967. As of January 1, 2026, the treaty binds 118 States Parties.
The treaty sets a clear rule for orbital weapons by banning nuclear arms and other weapons of mass destruction (WMD) in orbit while leaving conventional weapons permitted. Article IV explicitly prohibits placing weapons of mass destruction around Earth, installing them on celestial bodies, or stationing them in space. It reserves the Moon and other celestial bodies exclusively for peaceful purposes, while permitting orbital military reconnaissance, secure communications, and conventional defense hardware.
Outer Space Treaty Provisions Across the Primary Articles
The Outer Space Treaty establishes six core principles that govern national access, territorial claims, weapons deployment, and state liability beyond Earth. The United Nations Office for Outer Space Affairs (UNOOSA) maintains the primary treaty text and the treaty status table.
Article I establishes that the exploration and use of outer space shall be carried out for the benefit and in the interests of all countries, and shall be the province of all mankind. It guarantees that space remains free for exploration and use by all states without discrimination, and protects freedom of scientific investigation.
Article II addresses national expansion by barring sovereign claims over off-world territory. The exact text states: 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 IV divides orbital space from celestial bodies when regulating military activity. Paragraph 1 contains the orbital weapons ban:
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.
Paragraph 2 governs surfaces beyond Earth:
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.
Article VI holds governments responsible for national space activities, whether conducted by state agencies or commercial entities. Non-governmental activities require authorization and continuing supervision by the appropriate state party.
Article VII establishes international liability. A state party that launches or procures the launching of an object, or from whose territory an object is launched, is internationally liable for damage caused to another state party on Earth, in air, or in outer space.
Article IX mandates due regard for the interests of other states parties. States must conduct exploration to avoid harmful contamination of celestial bodies, avoid adverse environmental changes on Earth from extraterrestrial matter, and undertake international consultations before conducting activities that cause potentially harmful interference.
Ratification Records and State Signatories
The Outer Space Treaty recorded 118 States Parties and 23 unratified signatory states as of January 1, 2026. These figures come from UNOOSA document A/AC.105/C.2/2026/CRP.9/Rev.1, issued on April 17, 2026. The Arms Control Association listed 115 states-parties as of June 2024, but the UNOOSA 2026 status record reflects newer accessions.
Recent accessions confirmed by UNOOSA include:
- Colombia (ratification; entered into force March 21, 2024)
- Uzbekistan (accession; entered into force October 17, 2024)
- Latvia (accession; entered into force May 23, 2025)
- Malaysia (accession; entered into force October 21, 2025)
Article XIV names three depositary governments: the United Kingdom, the Russian Federation (succeeding the Union of Soviet Socialist Republics, or USSR), and the United States. Instruments of ratification and accession are deposited in London, Moscow, and Washington, D.C.
The U.S. Department of State archival record details the American ratification path. The United States signed the treaty on January 27, 1967. The U.S. Senate gave unanimous advice and consent on April 25, 1967, and President Lyndon B. Johnson ratified the agreement on May 24, 1967. The U.S. instrument was deposited on October 10, 1967, the date the agreement entered into force.
The major military space powers remain legally bound as full states parties. The UNOOSA status document confirms that the Russian Federation and China are full States Parties. The United Kingdom, France, India, Japan, Israel, North Korea (Democratic People’s Republic of Korea), and Pakistan are also states parties. Iran has signed the treaty but has not completed ratification.
Article XVI allows any state party to withdraw from the treaty one year after submitting written notification to the depositary governments. Article XV provides that amendments take effect for each accepting state once adopted by a majority of states parties.
Military Boundaries and Permitted Orbital Systems
The Outer Space Treaty prohibits nuclear weapons and other weapons of mass destruction from orbit while leaving conventional weaponry in Earth orbit unregulated by its text. This distinction is why reconnaissance, communications, and conventional defense satellites operate in orbit legally.
A Union of Concerned Scientists analysis confirms that 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. Ground-based, air-launched, and conventional space-based weapons remain unaddressed by the treaty text.
The Arms Control Association notes that the treaty does not define weapons of mass destruction, though the term is understood to cover nuclear, chemical, and biological arms. The treaty does not prohibit intercontinental ballistic missiles armed with WMD warheads from transiting through space along suborbital trajectories. While some analysts argue the phrase peaceful purposes could be interpreted to prohibit all military weapons, that view represents a minority interpretation rather than the enforceable treaty text.
The treaty permits several military systems in Earth orbit:
- Early-warning satellites tracking ballistic missile launches
- Secure military communication and data-relay satellites
- Positioning, navigation, and timing constellations
- Optical and radar reconnaissance payloads
- Conventional orbital interceptors and space control systems
Military personnel are also explicitly permitted on celestial bodies. Article IV allows military personnel to conduct scientific research or support peaceful missions on the Moon and other celestial bodies.
Treaties and Frameworks Across the Space Domain
Four related international agreements and non-binding frameworks expand upon the foundational terms of the 1967 treaty. These instruments clarify specific provisions regarding testing, environmental liability, surface resources, and operating norms.
| Instrument | Adoption or Launch Year | Legal Status | Parties and Signatories as of January 1, 2026 | Application to Major Space Powers |
|---|---|---|---|---|
| Partial Test Ban Treaty | 1963 | Legally binding treaty | In force October 10, 1963 | Banned nuclear test explosions in the atmosphere, outer space, and underwater |
| Liability Convention | 1972 | Legally binding treaty | 100 States Parties, 18 signatories | Expands Article VII procedures for space object damage claims |
| Moon Agreement | 1979 | Legally binding treaty | 17 States Parties, 4 signatories | The United States, Russia, and China are not parties; France is a signatory only |
| Artemis Accords | 2020 | Non-binding political principles | 72 national signatories as of September 14, 2026 | Led by the United States to operationalize Outer Space Treaty principles |
The 1963 Partial Test Ban Treaty opened for signature on August 5, 1963, and entered into force on October 10, 1963. The Outer Space Treaty preamble references UNGA resolution 1884 (XVIII) of October 17, 1963, which called on states to avoid placing nuclear weapons or WMD in orbit.
The 1972 Liability Convention opened for signature on March 29, 1972, and entered into force on September 1, 1972.
The 1979 Moon Agreement opened for signature on December 18, 1979, and entered into force on July 11, 1984. The major spacefaring nations have not joined it. The United States, Russia, and China are not parties. Saudi Arabia formally notified the UN Secretary-General on January 5, 2023, of its withdrawal from the Moon Agreement, which took effect on January 5, 2024.
OrbitalIntel’s pages on lunar resource extraction and asteroid resource extraction cover how companies and governments read Article II’s non-appropriation rule.
The Artemis program operates alongside the Artemis Accords, established on October 13, 2020, by the United States and seven partner nations. NASA states that the accords reinforce commitments to the Outer Space Treaty, the Registration Convention, and the Rescue and Return Agreement. Signatures have grown steadily:
- Mauritius became the 70th signatory on July 17, 2026
- Turkiye became the 71st signatory on August 31, 2026
- Djibouti became the 72nd signatory on September 14, 2026
China is pursuing its own crewed lunar landing goals.
Modern Arms Control Proposals and Diplomatic Deadlocks
Multilateral initiatives to expand the Outer Space Treaty into a binding ban on all space weapons have stalled across decades of diplomatic division. Proposals submitted to the United Nations have failed to bridge disagreements over verification and ground-based interceptors.
Russia and China submitted the draft Treaty on Prevention of the Placement of Weapons in Outer Space and of the Threat or Use of Force against Outer Space Objects (PPWT) to the Conference on Disarmament on February 12, 2008. They submitted a revised draft on June 10, 2014. The 2008 draft was rejected by multiple states on grounds that it lacked verification mechanisms. The Space Review wrote in August 2014 that the draft overlooked ground-based threats targeting orbit, including the ground-based weapon demonstrated in China’s 2007 anti-satellite test.
The United States formally detailed its objections at the Conference on Disarmament on August 14, 2019. Ambassador Robert Wood stated that the draft treaty remained fundamentally flawed, noting unresolved differences regarding weapon definitions and verification. Wood emphasized that the greatest operational threat to satellites comes from ground-based anti-satellite weapons rather than orbital platforms.
Diplomatic focus turned toward operational testing restrictions. On April 18, 2022, Vice President Kamala Harris announced that the United States would not conduct destructive direct-ascent anti-satellite (DA-ASAT) missile tests. On December 7, 2022, the UN General Assembly adopted resolution 77/41 calling on all nations to adopt identical commitments. The measure passed by a vote of 155 in favour, 9 against, and 9 abstentions. The nine dissenting votes were Belarus, Bolivia, the Central African Republic, China, Cuba, Iran, Nicaragua, Russia, and Syria. France became the ninth nation to formally join the U.S. pledge at that time.
The Security Council split again in 2024. As confirmed in United Nations reporting on the draft resolution, Russia vetoed a Security Council resolution on April 24, 2024. The measure, drafted by Japan and the United States, would have reaffirmed the Outer Space Treaty ban on placing nuclear weapons or WMD in orbit. The final vote recorded 13 in favour, 1 against (Russia), and 1 abstention (China).
The resolution followed a February 2024 U.S. intelligence disclosure indicating that Russia was developing a nuclear-armed anti-satellite capability. U.S. Ambassador Linda Thomas-Greenfield called the Russian veto a missed opportunity to rebuild trust in existing arms control obligations.
On-Orbit Defense Capabilities and Treaty Compliance
Deploying operational space control weapons in Earth orbit does not breach the Outer Space Treaty as long as those payloads exclude nuclear warheads and weapons of mass destruction.
On September 14, 2026, at the Air & Space Forces Association (AFA) Air, Space & Cyber Conference in National Harbor, Maryland, Air Force Secretary Troy Meink publicly confirmed operational deployments. As reported by Breaking Defense, Meink announced:
Today, we continue to ensure we remain ready to meet the challenges of evolving threats wherever they exist. This is why the United States now has on-orbit space control weapons capable of defending the joint force against hostile adversary actions.
Meink declined to identify the specific weapon types or deployment dates. When asked whether discussing orbital weapons publicly might embolden foreign adversaries, Meink pointed to existing foreign programs:
Is there any question in the room by anybody about whether or not the Chinese and Russians have been developing these sorts of weapons?
A Space Force spokesperson confirmed to The War Zone that space control encompasses kinetic and non-kinetic means to disrupt, degrade, or destroy adversary capabilities. The spokesperson stated that U.S. military operations comply with international law, including the Outer Space Treaty and the Law of Armed Conflict (LOAC).
News organizations covering the announcement, including CNN, Breaking Defense, and The War Zone, noted that the Outer Space Treaty does not prohibit conventional weapons in Earth orbit. Space defense analysts did not allege any treaty violation. Clayton Swope, deputy director of the Aerospace Security Project at the Center for Strategic and International Studies (CSIS), noted that possibilities include jamming satellites or orbital anti-satellite weapons. Victoria Samson, Chief Director at the Secure World Foundation (SWF), told CNBC the announcement was “a very destabilizing statement” that may be meant as a deterrent. Juliana Suess of the German Institute for International and Security Affairs observed that the disclosure confirmed an orbital basing mode without revealing technical specifications.
In the same address, Meink disclosed that a U.S. space-based interceptor effort moved from initial contract to flight-ready hardware in less than one year. That missile-defense program relates to the Golden Dome missile defense architecture rather than the space control weapons statement.
At OrbitalIntel, we track primary legal texts, United Nations documentation, and military policy disclosures to evaluate how defense programs align with international treaties.
Readers seeking a comprehensive ban on all orbital military hardware will not find it in the 1967 text, which leaves conventional military operations permitted. A formal amendment under Article XV or a newly ratified multilateral treaty banning conventional weapons in orbit would change this legal baseline, though no such measure has reached consensus among major powers.
To check any country’s status under the Outer Space Treaty yourself, open the UNOOSA treaty status table, which lists every party as of January 1, 2026.