Several European and NATO member states still govern territories far beyond their immediate borders.

From the Caribbean Sea to the Indian Ocean, parts of Europe lie thousands of kilometres from the continent, raising a basic but unresolved question: is there a collective mechanism for their defence?

In theory, a NATO state can trigger the alliance’s Article 5 to request assistance in the event it is attacked. But the collective defence clause doesn’t apply everywhere, and its geographical scope is actually defined in the much lesser-known Article 6.

It states that, for Article 5 to be triggered, an armed attack must occur “on the territory of any of the Parties in Europe or North America (…), on the territory of Turkey or on the Islands under the jurisdiction of any of the Parties in the North Atlantic area north of the Tropic of Cancer.”

NATO’s ultimate security guarantee, therefore, does not extend to a big part of Europe’s overseas territories. Can the EU’s mutual assistance clause fill the gap?

Unlike NATO’s Article 5, Article 42(7) of the EU Treaties is not a mutual defence clause but a mutual assistance clause. Nevertheless, it has no geographical limitation.

The EU’s mutual assistance is increasingly the subject of political debate in Brussels. Several member states remain cautious about its potential implications, particularly the risk that a more explicit reliance on EU mutual defence mechanisms could accelerate a planned US partial withdrawal.

EU diplomats are this week expected to run a simulation of the application of Article 42(7), which remains politically defined rather than clearly tested.

EU overseas territories

France is the EU member state with the most overseas territories. Below the Tropic of Cancer, and so outside of NATO’s Art. 5 scope, Paris controls French Guiana in South America, home to ESA’s European Spaceport. It also includes Guadeloupe, Martinique, Saint-Martin, and Saint-Barthélemy in the Caribbean. In the Indian Ocean, Réunion and Mayotte remain part of the French state.

Security of these territories is the responsibility of the French armed forces alone, but as part of the European Union, any armed attack could prompt Paris to activate the EU mutual assistance mechanism.

The Netherlands also holds Caribbean territories, including Aruba, Curaçao, Sint Maarten, Bonaire, Sint Eustatius and Saba. Speaking to Euractiv, a spokesperson for the Dutch Ministry of Foreign Affairs confirmed that these territories “fall outside the geographical scope” of NATO’s Article 5 because they lie south of the Tropic of Cancer.

“That being said, a provision like Article 5 is not necessary for allies to request or provide (military) assistance in the case of an armed attack on any of these territories,” the spokesperson added.

Unlike the French case, Aruba, Curaçao and Sint Maarten are autonomous countries within the Kingdom of the Netherlands. Asked about Article 42(7), the ministry said the provision “speaks for itself” and “should be understood as an expression of solidarity between EU member states”.

To better understand the Dutch Caribbean, the Greenland case offers a useful comparison.

Asked about the scope of EU assistance, the spokesperson confirmed that “Greenland is part of the territory of the Kingdom of Denmark and therefore covered by the mutual assistance clause.” In addition, Greenland sits well above the Tropic of Cancer, making it also eligible for NATO protection under its geographical framework.

Spain is another interesting case study regarding Article 6. Its exclaves of Ceuta and Melilla in North Africa appear to sit in a grey zone, as they lie outside Europe and North America. In 2022, ahead of the NATO summit in Madrid, the issue briefly surfaced in domestic political debate.

Spanish Prime Minister Pedro Sánchez dismissed the controversy. He said Spain had been a NATO member for over 40 years without such doubts ever being raised, stressing that “Ceuta and Melilla are Spain.” If the applicability of NATO’s Article 5 can be debated, there is no such ambiguity regarding the EU’s mutual assistance clause.

Non-EU overseas territories

The UK, a non-EU NATO member, retains 14 overseas territories under the sovereignty of the British Crown. They are spread across the Caribbean, Atlantic and Pacific Oceans. Most also lie outside NATO Article 5’s core geographic framing.

Recent geopolitical debate has, however, brought them back into focus. This includes renewed attention to the Falkland Islands dispute. In a recent internal email, first reported by Reuters, the US Department of Defence reportedly considered revisiting Washington’s position on island sovereignty, due in part to a perceived lack of support from the UK over the US-Israeli war in Iran.

British overseas territories, which fall outside NATO’s Article 5, rely solely on London for their protection.

The US also faces a geographic question. Hawaii lies south of the Tropic of Cancer. Territories such as Puerto Rico, Guam, the US Virgin Islands and American Samoa also fall outside the treaty’s traditional North Atlantic framing. They are therefore outside the strict geographic scope of Article 5 but can still count on NATO’s biggest army for their security.

This gap in the security understanding of overseas territories reflects the legacy of European states with global territorial footprints, even as their collective defence systems remain based on frameworks designed for a narrower Europe. This leaves responsibility for overseas territories occasionally unclear in the event of a crisis.

(at, cm)