Could an attack against a satellite trigger NATO’s art. 5?

Outer space, the new battlefield. Could an attack against a satellite trigger NATO’s art. 5?


10 | 02 | 2024


To solve part of the current indetermination, the new domain should be included in article 6 as another territory where an armed attack can take place

En la imagen

3D rendering of planet earth broadband internet system to meet the needs of consumers [freepick]

Space is becoming increasingly important in monitoring and assessing potential threats to national security. NATO itself recognized in 2021 during the Brussels Summit that application of article 5 of the Washington Treaty would be taken by the North Atlantic Council on a case-by-case basis. This paper examines to which extend it is feasible an application of article 5 in outer space and under which circumstances this should occur and explores if there are other international bodies that include outer space in their self and collective defense provisions.

Space is a new operational domain that plays a key role for security. It is crucial not only for military operations, but for other essential activities of modern life such as economic transactions, communication, weather monitoring, banking and agriculture. More specifically, in the military sector, space enables intelligence, surveillance, and reconnaissance (ISR) and contributes to early warning and secure communications capabilities. Altogether, space is becoming increasingly important in monitoring and assessing potential threats to national security. For this reason, the space domain is driving the attention of national security strategies and an increasing number of countries are launching satellites in order to satisfy its defense, economic, communication and environmental needs. In total, from the 8,261 satellites orbiting on Earth, 1,809 belonged to NATO allies in 2021. As a consequence, in 2019 NATO recognized space as an operational domain in par with the air, land, sea and cyber domains and implemented its Space Policy. This designation shows that NATO is aware of the growing role of space in its operations. In order to implement space as an operational domain, the Alliance is focused on maintaining situational awareness and reliable access to space services, so as integrating space in training and exercises.

It is expected the reliance of military operations on space assets and the role of space in future conflicts to increase in the following years. Therefore, another big step in relation to space was taken in 2021 during the Brussels Summit, where NATO leaders agreed that article 5 of the Washington Treaty could be invoked if “attacks to, from, or within space present a challenge to the security of the Alliance.” However, in that same summit it was highlighted that such application of Article 5 would be taken by the North Atlantic Council on a case-by-case basis.

Outer Space under article 5 of the Washington Treaty

Article 5 of the Washington Treaty says that if any of the NATO Allies suffers an armed attack, each and every member of the Alliance will consider it as an act of violence against all the members and consequently all the actions necessary to assist the Ally attacked. These actions they do not need to be military, but can consist in economic support, humanitarian assistance or other measures required. This action should finalize when the UN Security Council takes steps required to restore peace and security. Article 5 should be complemented with article 6, which accentuates that for the purpose of its application, the armed attack should take place on:

The territory of any of the Parties in Europe and North America

Algerian Departments of France

Territory of Turkey

The Islands under the jurisdiction of any of the Parties in the North Atlantic area of the Tropic of Cancer

The forces, vessels, or aircraft of any of the Parties, when in or over these territories or any other area in Europe in which occupation forces of any of the Parties were stationed on the date when the Treaty entered into force or the Mediterranean Sea or the North Atlantic area north of the Tropic of Cancer

However, article 6 leaves undetermined if outer space enters into the scope of application of article 5. Armed attacks occurring inside the airspace of NATO members would be considered to be occurring in Europe and North America, but it does not say anything about attacks taking place over those territories. Some analystsbelieve that the interpretation of article 6 is clear and imposes geographic limits that impedes its application in outer space. If satellites were included under this scope, many features would need to be determined. For instance, if attacks against space objects belonging to the Allies anywhere in orbit could be considered a degradation of NATO capabilities.

Self and collective defense in outer space under other legal bodies

Seeking for a more concrete answer in other international bodies shows that the European Union faces the same level of indetermination as NATO. Article 42 (7) of the Treaty on European Union states that “if a Member State is the victim of armed aggression on its territory, the other Member States shall have towards it an obligation of aid and assistance by all the means in their power, in accordance with Article 51 of the United Nations Charter.” Again, this article recalls that the aggression needs to take place on European territory, but does not determine the extension of these terms, assuming that it covers land areas, airspace and territorial waters of EU Member States. According to maritime law, article 42 (7) does not extend to international waters, but is only applicable under internal and territorial waters. This means that art. 42 (7) TEU could not be invoked if a European ship was attacked in international waters. Applying this same principle to outer space, it does not seem feasible that an attack to a European satellite that does not take place exactly when it is orbiting over European territory would enter under the scope of art. 42 (7) TEU.

In the case of cyberspace, another domain that is playing an increasing important role in the security field, mutual assistance remains also unclear. In the Vilnius Communiqué NATO stated that cyber activities could reach the level of armed attack, leading to the application of art. 5 on a case-by-case basis. In the European Union, in 2021 the Dutch Parliament called upon the government to advocate for the applicability of art. 42 (7) TEU to hybrid threats, but cyberattacks are as undefined as outer space attacks to this extent. Analysts point out that a cyber-operation should be considered an armed attack in the scope of art. 51 of the UN Charter if it results in significant death or injury to persons in order to trigger application of art. 42 (7) TEU. With regard to this, the General Assembly of the United Nations affirmed in 2015 that international law is fully applicable to cyberspace as much as to traditional conflict areas on land, sea and air.

Article 51 of the UN Charter is the root of article 5 of the Washington Treaty and article 42 (7) TEU. According to it, the right of self or collective defense is recognized to States if an armed attack occurs against them. In this sense, an armed attack should be understood as an international intervention against another State without that State consent which is not legally justified. In order to lawfully respond to an attack, the ICJ established in Nicaragua v. United States 1986 and in Iran v. United States 2003, that such a response should be on the observance of the criteria of necessity and proportionality. For these criteria to be met, force in self-defense may be used only when necessary to end an attack and when all peaceful means have been exhausted or are unavailable. Besides, the attack must be imminent, which requires the belief that any further delay will result in the inability of the defending State to defend itself from the attack. Both in the cases of cyberspace and outer space there exists the threat of an international intervention against a State without legal justification which delay can result in the inability of the State to defense itself. In such a circumstance, the criteria of art. 51 of the UN Charter would be met to apply art. 5 of the Washington Treaty and art. 42 (7) TEU.

In relation to the inability of the State to defend itself, what it is certain is that attacks on satellites have enormous consequences on Earth that most of people are not aware of. Satellites are a key component of global communication systems, a disruption in these communications would widespread outages in telephone, internet or television networks and individuals, businesses and emergency services would be affected. Navigation systems rely on satellites to provide GPS functions, an attack on satellites would disable these systems, so as the ability to prevent hurricanes or typhoons when talking about weather forecasting, where satellites play a critical role monitoring and providing data. Furthermore, in the event of an armed conflict, damage or destruction of a space object could generate the so-called space debris, which is spatial garbage, which can damage or destroy other satellites.

Application of article 5 on a case-by-case basis

Turning back to the 2021 Brussels Summit, where it was agreed that application of article 5 would be considered on a case-by-case basis by the North Atlantic Council, it is important to consider that all NATO decisions are made by consensus. This means that every agreement is reached by common consent, or in other words, that there is no voting. During this proceeding, consultations take place until a decision that is acceptable to all members is reached. In the case of an attack against an allied satellite this would signify that decision towards the application of article 5 of the Washington Treaty would have to wait until a consensus among all the 31 NATO Allies is reached. Taking into consideration the undefined terms of outer space attacks, this might happen rapidly or extend over time, which would affect an imminent response by Allies if required, or not happen at all.


It was not until 2019 that NATO recognized space as an operational domain in par with the air, land, sea and cyber domains and implemented its space policy. Therefore, it is comprehensible that Allies have not determined an adequate extension of article 5 of the Washington Treaty when applied to space. However, in order to the invocation of such article to be realistic, more details on its scope of application are needed. First of all, outer space should be included in article 6 as another territory where an armed attack can take place. Secondly, the circumstances of a collective defense response should be specified according to international law. Last but not least, decisions on invocation of article 5 should not be taken on a case-by-case basis, but automatically if the situation meets the legal requirements. In order of article 5 to be updated to the new circumstances, NATO needs to assume that the current world faces challenges that hugely differs from those occurring when the Treaty of Washington was written at the end of the 1940s.