Historical context

Article 42, paragraph 7, of the Treaty on European Union (TEU), succinctly Article 42(7) (see Box 1), is also known as the EU’s “mutual assistance clause” or is sometimes even referred to as its “mutual defence clause”. Its origins date back to the early 1950s, and more specifically to the Pleven Plan[6] for the establishment of the European Defence Community (EDC). Even though this was followed up by the signing of the Treaty establishing the EDC in 1952, the Plan never materialised as the EDC failed.

A new attempt, however, turned out to be more successful. In 1954, the Paris Accords led to the drafting of the modified version of the Brussels Treaty (1948), which already contained a mutual defence clause in Article IV. The Paris Accords then paved the way for the establishment of the Western European Union (WEU), which built upon the Brussels Treaty’s basis for mutual defence between European states outside the NATO framework. Of particular relevance in this regard is the wording of Article V of the Modified Brussels Treaty, the mutual defence clause of the WEU (see Box 2).[7] Article V lays down the ‘High Contracting Parties’ obligation to assist any other ‘High Contracting Party’ that becomes the object of an armed attack. Moreover, the Article explicitly refers to ‘military assistance’ as one of the means to be used to assist a state in case of an armed attack. It nonetheless remained dormant, largely because the centre of gravity of European collective defence shifted to NATO.

The launching of the European Security and Defence Policy (now the Common Security and Defence Policy, CSDP) in 2000 led to the gradual transfer of WEU institutions into the EU. The forthcoming dissolution of the WEU did confront policymakers with the question of the fate of its mutual assistance clause in Article V. In 2007, the mutual assistance clause was incorporated as Article 42(7) in the Lisbon Treaty, although in an amended form. When the Lisbon Treaty entered into force in 2009, the EU had thereby formally obtained its own mutual assistance clause. Consequently, the Modified Brussels Treaty was terminated.

As compared to the original WEU version, the mutual assistance clause in the TEU slightly differs. Firstly, where the WEU version referred to an ‘armed attack’, the TEU refers to ‘armed aggression’. This begs the question whether Article 42(7) provides a broader scope than its predecessor. However, the reference to ‘armed aggression’ may also simply be the result of a literal translation of the French text. The French text refers to ‘aggression armée’, the wording of the French version of Article 51 of the UN Charter, which in English refers to an ‘armed attack’.[8] For the purposes of this report, the two concepts of ‘armed aggression’ and ‘armed attack’ will therefore be used interchangeably. Secondly, the WEU version explicitly mentions ‘military assistance’ as a means to be deployed in case of an armed attack. In contrast, this has been discarded in the TEU version, which only refers to assistance “by all the means in their power”. Even though this may also include military means, the lack of an explicit reference thereto might be a way to meet neutral states like Austria, Ireland and Sweden halfway.[9] Finally, the article also includes an explicit mention that for those EU member states that are also NATO allies, NATO remains the ‘foundation of their collective defence’. The complex relationship between the EU’s Article 42(7) and NATO’s Article 5 will be further discussed below.

Legal context and relationship to other treaty articles

Following France’s invocation of Article 42(7), the Political and Security Committee (PSC) requested the Legal Services of the Council to provide advice on the nature of the obligations arising under Article 42(7).[10] Other scholars have also explored various legal aspects. While this report focuses primarily on strategic considerations around Article 42(7) and does not intend to deliver a comprehensive legal analysis, in their attempts to operationalise the article EU member states should take its relationship to other EU and international treaty articles into account. These particularly concern Article 51 of the UN Charter, the EU’s ‘solidarity clause’ (Article 222 TFEU), and NATO’s Article 5. Each will be briefly discussed in turn.

Relationship with Article 51 of the United Nations Charter

Article 42(7) makes explicit reference to the UN Charter by stating that the assistance provided by the EU member states in case of an invocation of Article 42(7) should be in accordance with Article 51 of the Charter (see Box 3). The reason for this explicit reference is that Article 51 is the leading international treaty article that guides the invocation of individual and collective self-defence in the case of an armed attack against a member of the UN. The explicit reference implies that any action that is undertaken by an EU member state in response to the invocation of Article 42(7) will be legally assessed in light of Article 51. As such, the relationship between Article 42(7) and Article 51 is similar to the relationship between Article 5 NATO and Article 51 of the UN Charter: both the EU and NATO provisions are an expression of individual or collective defence against an armed attack as set forth in Article 51[11]. Hence, the use of force as an expression of the right to collective self-defence under either Article 5 of NATO or Article 42(7) of the TEU remains subject to international law. This includes the requirements of necessity and proportionality, although these principles are not explicitly part of the UN Charter.[12]

Importantly, Article 51 of the Charter includes the right for states to defend themselves against an imminent attack, which is more commonly referred to as anticipatory self-defence. Anticipatory self-defence should not be confused with pre-emptive self-defence: the former refers to self-defence in case of an imminent attack while the latter entails self-defence that is focused on removing a potential threat before it can manifest itself to the level of an attack. Even though opinions on what constitutes an ‘imminent’ attack diverge, anticipatory self-defence is considered to be legal, subject to certain criteria, while pre-emptive self-defence violates international law.[13]

Moreover, since 9/11, the common view is that international law acknowledges that an armed attack executed by non-state actors might, under specific circumstances, also trigger the invocation of national or collective self-defence. Hence, this argues in favour of the possibility for EU member states to invoke Article 42(7) against an (imminent) attack or aggression by both state and non-state actors, as illustrated by the case of France responding to the Bataclan attacks.[14]

Relationship with Article 222 TFEU

Article 222 of the Treaty on the Functioning of the European Union (TFEU) prescribes that EU member states have to act in a spirit of solidarity if a fellow member state becomes the victim of a terrorist attack or a natural or man-made disaster (see Box 4). The article is therefore known as the “solidarity clause”. Considering that Article 222 explicitly refers to terrorist attacks, the invocation of Article 42(7) by France after Bataclan in 2015 sparked a debate about the question of in which situation a member state should invoke Article 42(7) TEU or Article 222 TFEU. In essence, this comes down to a choice for the member state concerned about the nature of the threat it faces and the kind of response it wishes to elicit. France’s invocation of Article 42(7) was in response to an attack by non-state actors, thereby establishing a precedent for relying upon Article 42(7) if the perpetrators are non-state actors.[15]

There are, however, some important differences between Article 42(7) TEU and Article 222 TFEU, which might affect the decision of member states to invoke either of the articles. Firstly, Articles 222 TFEU and 42(7) TEU differ in the sense that the former explicitly calls upon the Union to mobilise all the instruments at its disposal. Therefore, upon the invocation of Article 222, the EU as an institution is supposed to take the necessary measures. Moreover, the operationalisation of Article 222 is already codified in the ‘Council Decision on the arrangements or the implementation by the Union of the solidarity clause’.[16] In contrast, Article 42(7) is fully member state-driven and there is no formal EU procedure that regulates the involvement of the EU institutions. Instead, the invocation of the article initiates an intergovernmental process in which the responsibility lies squarely with the EU member states themselves, and it is eventually up to them to decide on providing assistance – or to request the involvement of the institutions.[17] This aspect will be further discussed in Chapter 5.

Secondly, an important consideration upon invoking either Article 42(7) or Article 222 revolves around the difference in agency of the affected member state. In case a member state invokes Article 222[18], that state formally acknowledges that it is being overwhelmed by the attack or disaster and admits that it lacks the necessary means to act on its own. For political reasons, this might be unattractive to the member state in question. Considering that Article 42(7) does not have such a clause in its provision and puts the member state in the driving seat, especially the larger EU members might give preference to invoking this article instead.[19] This logic may also work in the inverse for smaller member states, which might need more assistance from EU institutions in the coordination and provision of assistance. Some of the EU’s traditionally neutral member states might also prefer to shy away from requesting military means for the purpose of collective defence and would rather solicit assistance of a non-military nature. In both cases the affected member state could consider opting for Article 222 instead.[20]

Relationship with Article 5 of the North Atlantic Treaty

As mentioned, when the text of the WEU version of the article was amended and included in the Lisbon Treaty as Article 42(7), it was supplemented with an explicit reference to NATO: “Commitments and cooperation in this area shall be consistent with commitments under the North Atlantic Treaty Organisation, which, for those States which are members of it, remains the foundation of their collective defence and the forum for its implementation.”[21] By explicitly including this clause in Article 42(7), it is acknowledged that for those EU member states that are also members of NATO, the North Atlantic alliance is the primary organisation for guaranteeing collective defence. However, this does not mean that the EU cannot play a role in collective defence at all, which is in particular relevant to those member states that are not part of NATO. The question therefore remains what the link between the two treaty articles is. It is clear that the invocation of one of these provisions does not automatically result in the invocation of the other. It is up to the member states of both organisations to decide which of the two articles they wish to invoke in case of an attack.[22]

Moreover, there are two important differences between Article 42(7) TEU and Article 5 of the North Atlantic Treaty (see Box 5). These differences relate to the obligations in terms of their effect and the scope of both provisions. Firstly, NATO’s mutual defence clause with the phrase “as it deems necessary” leaves more room for national discretion than the EU’s Article 42(7). This implies that, although a response from each member state is required in case of the invocation of Article 5 of the NATO treaty, it is up to the member states to decide the nature of that response. In contrast, the EU’s mutual assistance clause is of a more compelling nature, as it states that member states have “an obligation” to provide “all aid and assistance by all the means in their power”. Secondly, the scope and the applicability of the provisions laid down in Article 42(7) TEU and Article 5 of the North Atlantic Treaty differ. Whereas the latter applies to all NATO member states, Article 42(7) specifically acknowledges the special status of neutrality that some EU member states have with respect to the EU’s security and defence policy (e.g. the Danish opt-out and the neutrality of states like Ireland, Malta and Austria): “This shall not prejudice the specific character of the security and defence policy of certain Member States.”[23] Article 42(7) also has a different and somewhat stricter interpretation of ‘territory’, as will be further discussed in the next chapter.