As a clause that is meant to be invoked only as the ultima ratio in response to an act of armed aggression, Article 42(7) TEU will never be a popular part of the EU treaties. Many member states are reluctant to engage in difficult discussions to operationalise their binding commitments towards one another. They are right to point out that the EU is neither designed nor currently equipped to operate as a military alliance. For 21 of its member states also member of NATO, the Alliance remains the cornerstone of collective defence in Europe. Article 42(7) is not the EU’s direct equivalent of NATO’s Article 5 and should not be misinterpreted as such. It is deliberately drafted in a different manner and it refers explicitly to NATO and the policy of neutrality of some EU member states. Instead of strictly positioning Article 42(7) as a competitor to NATO’s Article 5, for states that are members of both organisations it would be more logical to look at the article from the perspective of complementarity, based on the growing realisation that framing the dilemma as ‘EU or NATO’ is not only outdated but even harmful for both organisations. Instead, more cooperation between both organisations that draws on the strengths of both is essential to ward off modern threats.

In addition, an article rooted in the concept of collective self-defence should never be invoked lightly, should not be misused for short-term political purposes and the response to an invocation of Article 42(7) should always comply with Article 51 of the UN Charter and the internationally agreed principles of necessity and proportionality. The EU has many other instruments at its disposal that can be used to respond to a variety of threats and crises. One of these instruments is the solidarity clause of Article 222, even if that article might not be very appealing to certain member states due to the requirement to admit that they are overwhelmed.

Article 42(7) presents the EU with additional challenges. Among others, the threshold for what amounts to ‘armed aggression’ is deliberately kept ambiguous; moreover, the article has its roots in the early 1950s and its strict limitation to ‘territory’ raises questions as to its applicability to modern threats in cyberspace – or space itself.

But merely pretending that Article 42(7) does not exist – or attempting to neuter its deeply political character by hiding behind purely legal arguments – are neither realistic nor desirable policy options. The cases of France invoking it in 2015 and Greece’s consideration to do so in 2020 show that the EU’s mutual assistance clause is likely to be ‘here to stay’. If anything, it is a legal argument buttressing the growing political ambition towards a more strategically autonomous European Union that aims to defend its own members and interests in an uncertain and unsafe world. Rather than a cause for handwringing and concern, Article 42(7) is therefore yet another reason for the EU to reflect seriously, including within the process of the Strategic Compass, on the threats that its members face – and to accordingly increase their preparedness to assist one another in case of an act of armed aggression.

This paper concludes that there are at least three plausible sets of situations in which Article 42(7) TEU could legitimately be invoked: in response to a terrorist attack, against hybrid forms of aggression such as cyberattacks, and as a result of a conventional military attack. There are EU member states that are not members of NATO which might want to rely on the Article as a means of last resort, or there are even some calamitous cases that are thinkable in which one NATO ally could invoke it against another. As uncomfortable and hypothetical as these scenarios may be, the EU should nonetheless be prepared to respond in case they do materialise. The following policy recommendations could therefore be considered by the Government of the Netherlands and other EU member states:

Although some member states would like to see more clarity on the conditions under which Article 42(7) could be invoked, it is ultimately a political choice for a member state to resort to it – and for others to choose what assistance they provide. Everything really does depend on the political and security context at the time, as clichéd and unsatisfactory as this may be. Flexibility and a degree of strategic ambiguity are therefore essential. The Netherlands should acknowledge that clarifying and operationalising the article by way of a Council Decision with the introduction of cumbersome procedures or negotiations on fictional thresholds will not only be virtually impossible, it may even be counterproductive.

That said, strategic ambiguity and context dependency should not be a fig leaf for EU member states to hide behind to avoid discussing the article altogether. Instead, due to the hypothetical ‘what if’ nature of the article, scenario-based discussions, tabletop and live exercises such as those organised by the PSC throughout 2021 can serve as a means to align the expectations that EU member states have of one another. These exercises can contribute to more preparedness and awareness, and can thereby ideally lead to a gradual convergence of positions that now still seem far apart. The exercises should not be confined to the PSC; they could also be conducted jointly with the EU Military Committee. Ideally, the possible invocation of Article 42(7) should be incorporated in other EU exercises, including in responding to cyberattacks and/or other forms of hybrid threats. The Netherlands could take a leading role in this regard by advocating more and better integrated EU tabletop and live exercises, including jointly with NATO.

A proactive and appropriate response to many of the hybrid threats that could lead to an eventual invocation of Article 42(7) would require more sharing of intelligence among EU member states, which would depend, among other things, on developing a trusting relationship. Better infrastructure for secure communications of classified information is essential in this regard. Improved cooperation in the EU context to increase common attribution capabilities of cyberattacks would also be helpful, including to increase the deterrent value of Article 42(7) towards perpetrators. In addition, the Netherlands could push for addressing the matter of mutually reinforcing assistance to member states in case of cyberattacks in an eventual new EU-NATO Declaration.

Acknowledging that the EU has a vast toolbox at its disposal to respond to various threats, including in the context of Article 42(7), the EU member states – including the Netherlands – should actively contribute to and make maximum use of the non-binding document that is being developed by the EEAS based on the scenario-based discussions held in 2021. This document should not become a strict set of definitions and procedures or a re-run of the 2016 Legal Opinion of the Council’s Legal Services but should instead serve as an operational tool that member states can use to identify which EU institutions and instruments they could potentially involve and how they could do so in practice. This should include potential responses to the invocation of the article in the face of serious hybrid threats, as already suggested by Federica Mogherini in 2016 and by the Dutch Parliament in 2021.

As a treaty commitment of EU member states towards one another, Article 42(7) is and should remain strictly member state-driven. This is not to say that the EU institutions should never have a role to play. For example, the invoking member state or the European Council can endow them with a mandate to act as 1) a ‘clearing house’ that keeps track of assistance provided by other member states, 2) a coordination mechanism for support from various EU institutions, or 3) an external communicator towards other multilateral organisations. Their exact role will depend on the context, the type of aggression faced by the member state and its request. No new EU structures need to be created for this purpose, but the Netherlands could advocate that existing structures should be prepared in case a request in the context of Article 42(7) is made. A Mutual Assistance Task Force (MATF) can be established and led by the EEAS Deputy Secretary-General for CSDP and Crisis Response with the participation of the EU Military Staff, relevant Commission agencies such as Frontex and ENISA and other EEAS departments such as ISP, StratCom and SECDEFPOL. To increase preparedness, it would be beneficial for such a task force to convene regularly and take part in relevant exercises.

Although the EU has no ‘NATO Article 4’ consultation mechanism, the invocation of Article 42(7) should not come as a surprise to other member states. Strictly speaking the European Council only has to take note of the invocation of the article. Unlike NATO’s Article 5, it does not need to be formally activated by a unanimous decision. Legal principles aside, a swift, credible and united EU response should nonetheless ideally be articulated through a statement by the European Council, which would still require consensus. If time allows, it is therefore far preferable for member states to engage in bilateral and multilateral consultations prior to the invocation of the article, in particular within the PSC. The Netherlands could suggest models of how the PSC and other relevant committees could be convened at the shortest possible notice for this purpose and could promote preparedness through the abovementioned exercises.

Finally, Article 42(7) deserves a modest but nonetheless visible place within the broader discussions on European security and defence, especially in the context of the Strategic Compass and related investments such as within Permanent Structured Cooperation (PESCO). Despite the ‘grey zone’ nature of the threats facing the EU member states, the article is a black-and-white codification of their shared fate and their binding commitment to assist one another in the case of armed aggression. As such, Article 42(7) should serve as yet another powerful reminder to EU member states that they should invest considerably more in their defence capabilities. This acutely applies to the Netherlands, which not only lags behind in meeting its defence expenditure commitments but is also rather modest when it comes to its contributions to CSDP missions and operations. Capabilities are key to the credibility of mutual assistance arrangements. While policymakers and citizens across the entire European Union may prefer that the article would never be invoked again and may continue to hope for the best, it is better to prepare for the worst.