Written by Anthony Phan

Introduction

On October 10, 1967, the United Nations (“U.N.”) entered into force the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies (“Outer Space Treaty”).¹See Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies, Jan. 27, 1967, 610 U.N.T.S. 205 [hereinafter Outer Space Treaty].The Outer Space Treaty, known as the “Magna Carta of Space,” was the first international space treaty.²See generally A Timeline for the Exploration and Use of Outer Space, Office of Outer Space Affairs, https://www.unoosa.org/oosa/en/timeline/index.html (presenting a chronology of the exploration and use of outer space) (last visited Oct. 3, 2025). Requiring all State Parties to explore and use outer space, including the moon and other celestial bodies, for “peaceful purposes,” the Treaty, however, lacked a clear definition for what peaceful exploration and use entail.³See Outer Space Treaty, supra note 1. This legal void may prove problematic for international peace and security as state and non-state actors enhance their space capabilities and military or commercial activities in outer space, potentially preparing for armed conflict or conduct that otherwise does not conform with international laws and principles.⁴See Jeremy Grunert, The “Peaceful Use” of Outer Space?, War on the Rocks (June 22, 2021), https://warontherocks.com/2021/06/outer-space-the-peaceful-use-of-a-warfighting-domain (warning that, as China and Russia increase their military space activities, concerns about the peaceful exploration and use of outer space will become more pronounced).

The U.N. Charter, Outer Space Treaty, and Moon Agreement 

The primary source for defining the term “peaceful” is the founding document of the United Nations: the U.N. Charter (the “Charter”), ratified on October 24, 1945, after the Second World War.⁵See U.N. Charter.  The Charter, which established the United Nations, primarily was signed “to save succeeding generations from the scourge of war.”⁶See id.  Among the purposes of the United Nations are “equal rights and self-determination of peoples,” which serve the purpose of developing “friendly relations” between nations.⁷See id. at art. 1, par. 2. In pursuit of this purpose, Members must adhere to several other principles, including “settl[ing] their international disputes by peaceful means,” so as not to endanger international peace and security and justice.⁸See id. at art. 2, par. 3. Members can resolve disputes peacefully by refraining “from the threat or use of force against the territorial integrity or political independence” of any nation.⁹See id. at art. 2, par. 4. Territorial integrity is not yet an issue in outer space, due to the prohibition on claims of sovereignty over celestial bodies,¹⁰See Outer Space Treaty, supra note 1, at art. 2. Following the U.N. Charter’s language in Article 2, however, any definition for “peaceful purposes” should make mention of protecting against the “threat or use of force” in the space domain.¹¹See U.N. Charter, supra note 5, at art. 2, par. 4.

            The Outer Space Treaty provides a basic framework on international space law, including general principles on exploring and using outer space.¹²See Outer Space Treaty, supra note 1. These principles encourage free exploration and use that benefit all nations, prohibiting national appropriation and nuclear weapons programs in outer space, as well as pollution thereof.¹³See id. Article I requires “freedom of scientific investigation” and “international co-operation in such investigation” in outer space.¹⁴See id. at art. 1, par. 3. Although nuclear research may be considered scientific, Article IV prohibits States from “plac[ing] into orbit . . . nuclear weapons or any other kinds of weapons of mass destruction, install[ing] such weapons on celestial bodies, or station[ing]” them in outer space.¹⁵See id. at art. 4, par. 1. This article further forbids the “establishment of military bases, installations and fortifications, the testing of any type of weapons and the conduct of military manoeuvres on celestial bodies.”¹⁶See id. at art. 4, par. 2. Together, the two paragraphs of Article IV lay the groundwork for what activities constitute non-peaceful purposes.¹⁷See id. at art. 4.

The Moon Agreement reaffirms many provisions of the Outer Space Treaty, aiming “to prevent the Moon from becoming an area of international conflict.”¹⁸See Agreement Governing the Activities of States on the Moon and Other Celestial Bodies, Dec. 5, 1979, 1363 U.N.T.S. 3 [hereinafter Moon Agreement]. Though echoing the Outer Space Treaty’s prohibitions on military structures and operations, Article 3 of the Moon Agreement has no prohibition on the presence of military personnel on the Moon.¹⁹See Moon Agreement, supra note 22, at art. 3, par. 4.Neither does this article prohibit the “use of military personnel for scientific research.”²⁰See id. This article also does not prohibit States from using “any equipment or facility necessary for peaceful exploration and use” yet stops short of explaining what things might be necessary for such a purpose.²¹See id.This ambiguity provides another reason for why the U.N. should obtain consensus on the meaning of “peaceful purposes.”

Drawing from the language and context of these legal instruments, this author proposes the following definition for adoption by the U.N. General Assembly (“G.A.”): Peaceful purposes for the exploration and use of outer space involve non-hostile and non-aggressive activities, conducted in a manner that constitutes no threat or use of force against the national security or sovereignty of any State, such as conventional weapons deployment,  and that adheres to international law and to U.N. principles, in the common interest of humankind, including, but not limited to, scientific and technological research, astronaut rescue and assistance, private space travel and entrepreneurship, environmental protection, or similar endeavors that advance human progress and development through cooperation and mutual assistance.

International Cooperation to Prevent Armed Conflict Within and Beyond Earth’s Orbit 

The U.N. should define “peaceful purposes [or uses]” for the exploration and use of outer space because, whereas the Outer Space Treaty and Moon Agreement prohibit weapons of mass destruction, for example, the legal instruments do not address other conventional weapons in space.²²See Abdulla Alkhaja and Rashed Al Hosani, Ambiguity in Orbit: The Blurred Lines Between Peaceful and Military Uses of Outer Space, Trends Research & Advisory, (September 2025), https://trendsresearch.org/insight/ambiguity-in-orbit-the-blurred-lines-between-peaceful-and-military-uses-of-outer-space/?srsltid=AfmBOorxAvG4Q_mDJEqmYXLuLx1OROkUhFB9MRpAaH1t2wVb0Z8CgeR3 (emphasizing that, without reasonable limitations in the international space law regime, outer space will become a battlefield among nations). The U.N. can accomplish this effort by addressing the need for a definition during a G.A. session. The U.N. should then move to adopt a resolution and have nations with space programs join that resolution. Already, state actors have begun testing anti-satellite weapons, fueling fears over the weaponization of outer space.²³See Chris O’Meara, Balancing State Security and Peace and Security in Outer Space: What Role for International Law on the Use of Force?, Just Security, (April 2025), https://www.justsecurity.org/110248/security-outer-space-international-law(urging States and other interlocutors to work toward restraining military activities in outer space). To prevent armed conflict in the space domain, the U.N. should, during a G.A. session, address the lack of a clear definition for “peaceful purposes” and thereby underscore the need to articulate such a definition, if the international community is to preserve outer space as a peaceful domain.

The U.N. should call on leaders in outer space, such as the United States, Japan, Russia, and China, including States that do not yet have robust space programs but wish to develop such programs, to set the standard for what peaceful uses and activities might entail. Only through mutual effort would the international community achieve this ambitious goal. Once the importance of articulating a definition becomes apparent, the U.N. should move to adopt a resolution for countries with space programs to join. In accordance with its functions and powers set forth in the U.N. Charter, the G.A. should call to the Security Council’s attention the situations in outer space that endanger international peace and security.

Conclusion

The lack of a clear, articulate definition for “peaceful purposes” in international space law creates a legal void that leaves much room for interpretation, allowing adversarial nations to escalate their exploration and use of outer space toward hostile and aggressive conduct. The specter of armed conflict in this new frontier is too great a risk as a Space Arms Race looms on the horizon, especially with China and Russia at the forefront. Consensus on “peaceful purposes” by the signatories of major international space law treaties and agreements would hold considerable weight for key decision-making and would promote effectiveness and efficiency in outer space activities. With greater clarity and proper application of a workable definition for “peaceful purposes,” the space domain can represent a vista of human prosperity and lasting peace.