The European Union’s shaken confidence in Washington’s commitment to NATO has prompted calls to re-examine the bloc’s own mutual‑defence clause.

US President Donald Trump’s threat to take over Greenland from his NATO ally Denmark has spurred calls in Europe to revive the EU’s defence clause, Article 42.7 of the European treaties, something few in Brussels had previously considered.

“The Greenland incident changed thinking about NATO Article 5 and US reliability. So, we have our own solidarity clause which hasn’t been operationalised,” said Klaus Welle, a long-time Brussels insider who served as secretary‑general of the European Parliament for 14 years.

The European Union established Article 42.7 in the mid-2000s, but it has so far existed mostly on paper. While the article requires EU countries to come to the aid of other EU members in need, there’s much ambiguity over what that means.

The EU’s Defence Commissioner, Andrius Kubilius, has pushed for a clearer definition of Article 42.7 of the European treaties for some time. In January, following diplomatic fallout over Greenland, members of the European Parliament similarly began calling for greater clarity around the defence clause’s purpose.

Following similar statements from both Commission President Ursula von der Leyen and German Chancellor Friedrich Merz during the Munich Security Conference in February, the discussion gained real political traction.

Article 42.7 vs Article 5

Europe’s mutual‑defence clause leaves the decision over what assistance each EU country provides up to national capitals, similar to NATO’s Article 5.

However, some experts see Article 42.7 as even more far‑reaching than NATO’s collective defence commitment.

For one, the threshold to trigger the EU defence clause is lower, as it can be activated if an EU country faces armed aggression, such as a naval blockade. NATO’s clause, however, requires an armed attack. In addition, NATO’s defence clause only comes into effect if all 32 member states agree.

EU states are also obliged to support each other “by all means in their power,” while NATO’s provision calls for assistance as each ally deems necessary.

Despite the apparently wide-ranging nature of the EU’s mutual defence agreement, Welle – who currently leads the centre‑right Martens Centre advisory council and advises the Commission on defence matters – said it’s unclear what the response would look like if a country actually triggered Article 42.7.

For example, if 100,000 Russian troops suddenly appeared on the eastern border of one of the Baltic countries and the US, for whatever reason, signalled it would not engage in conventional defence under Article 5, there are questions over how the European Union would act, according to Welle.

“Europeans have to say what would happen exactly if Article 42 were activated,” Welle said.

The French test

The mutual defence article has only been activated once – by France after the Paris terrorist attacks of 2015. EU countries offered mainly logistical support, with Belgium and Germany sharing intelligence, police support and counter‑terrorism experts.

Greece also contemplated activating Article 42.7 in 2020, when it faced aggressive behaviour from neighbouring Turkey over maritime disputes in the Eastern Mediterranean.

The case was considered more complex because Turkey is a NATO member, and activation of Article 42.7 could escalate tensions between allies. There was also no political appetite in Brussels to escalate. At the time, Athens requested sanctions against Ankara, which were rejected by several countries, including Germany.

European autonomy

With the US planning to hand over more of Europe’s defence to Europeans, the possibility that NATO’s strongest member will largely stay out of potential conflicts on the continent’s eastern border with Russia is increasingly being considered.

For Luigi Scazzieri, an expert at the EU Institute for Security Studies, the EU should develop “ideas about what the EU as an institution can do to deter war.”

Such an exercise could involve the EU’s legal services agreeing on the geographical scope, said Scazzieri, whose institute is an EU agency that advises member states on foreign affairs.

Nonetheless, as long as NATO exists, it will remain the primary framework for Europe’s defence, Scazzieri noted. According to him, the EU’s focus over the next year will be on how, as an institution, it can support its member states in the event of an attack.

(cm, aw)