The United States' escalating threats over Greenland have revived scrutiny of Europe's mutual defence clause — and with it, uncomfortable questions about the bloc’s ability to face armed aggression on its own.
Introduced with the Treaty of Lisbon nearly two decades ago, the so-called Article 42.7 was originally championed by a handful of member states, including Greece, which at the time was seeking additional security guarantees amid tensions with Turkey. Mostly, the clause was conceived as a political backstop rather than a serious alternative to the North Atlantic Treaty Organization (NATO).
Today, however, as EU leaders increasingly line up behind a more strategically autonomous Europe, the clause is being reassessed with real deterrence and military readiness in mind.
“Uncertainty of the future of the transatlantic partnership demands our resolve,” the EU’s Defence Commissioner, Andrius Kubilius, said earlier this month.
The question is how far that resolve can extend in practice, and whether Article 42.7 can deliver more than political symbolism when its most needed.
What does the article say?
The EU’s mutual defence clause states that if a member state is the victim of an armed aggression on its territory, its counterparts have “an obligation of aid and assistance by all the means in their power.”
Such assistance could range from diplomatic support and medical assistance to civilian or military aid — meaning neutral countries such as Ireland or Cyprus wouldn’t be required to abandon their commitments.
Article 42.7 is automatically triggered once a member state decides to invoke it following armed aggression. NATO’s Article 5 works differently: it, requires the North Atlantic Council to unanimously agree an attack against one ally constitutes an attack against all before proceeding with a collective response.
However, the bigger difference isn’t how the articles are activated but what follows.
“It [Article 42.7] lacks the same decisiveness,” said MEP Riho Terras (EPP, EE), vice chair of the Security and Defence Committee. “And the EU does not possess the same centralised military command structures or action mechanisms as NATO.”
The clause itself acknowledges this reality, stating that for the 23 EU member states that are also NATO allies, the transatlantic alliance “remains the foundation of their collective defence and the forum for its implementation.”
As such, what makes the clause distinctive is that once it is invoked, without requiring unanimity, it bypasses EU institutions, leaving responsibility to act with each member state.
Would it be applicable to Greenland?
The clause covers both conventional and unconventional attacks, including cyber, hybrid and space attacks, as well as state-sponsored and non-state-sponsored terrorism. Yet it has only been invoked once, following the Paris terrorist attacks in November 2015.
At the time, France asked its EU partners to contribute resources to the international fight against terrorism, allowing it to reinforce domestic security with around 10,000 soldiers and 4,700 police officers and gendarmes.
But Greenland presents a more complex test case. The territory isn’t part of the EU but an autonomous region within the Kingdom of Denmark, which is both an EU and NATO member.
While Trump said at the World Economic Forum in Davos on Wednesday that he wasn’t planning to use military force to assert control over Greenland, the episode has nonetheless sharpened concerns in Brussels about how the EU would respond if pressure were to escalate beyond political or economic means.
Kubilius has said the EU’s mutual defence clause would definitely apply, Ursula von der Leyen — although vowing support for Greenland — has not given a straight answer to how it pertains to Article 42.7. An EU spokesperson later clarified that, in principle, it would apply.
That would depend on if Denmark choosing to invoke it, Gesine Weber, senior researcher at ETH Zurich, told The Parliament.
“If there is political will and the necessary capability, there can be a swift and effective response,” she said, but added that in the case of Greenland, she doesn’t expect such a response.
Similarly, Philip Bednarczyk, Warsaw office director of the German Marshall Fund, said some member states would be unlikely to act due to domestic political consideration linked to Washington, while others would fear jeopardising US support for Ukraine.
In his view, the EU should rely on its economic leverage, while continuing to build up its security structures over the long term.
Does Article 42.7 need updating?
The article itself does not define how it should be implemented — a flexibility that some see as a strength, and others as a weakness.
“There needs to be intergovernmental coordination and understanding when and how member states should support others,” Weber said. At present, she added, there is neither clear political signalling that the EU would act once a red line is crossed, nor the capabilities to do so.
Despite these shortcomings, most analysts and EU policymakers argue against reopening the treaty text itself.
“I see no viable option in Treaty modifications,” Terras said. “This would require a consensus among the member states, [and] we do not need another endless dividing discussion.”
As Kubilius said in a speech in Sweden earlier this year, the more pressing issue is how the EU can ready itself for activating article 42.7, and who would coordinate such a response.
That coordination could involve the EU’s own institutions, should the member state under attack request it. The broader question of readiness, however, may remain unanswered until the EU unveils its forthcoming security strategy.
Why is this, given that it’s clearly stated as an obligation. Didn’t you mentioned in your first draft that the language is actually more direct and harsher?
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