Solidarity Clause

The Solidarity Clause is set out in Article 222 of the Treaty on the Functioning of the European Union (TFEU), introduced by the Lisbon Treaty, which entered into force on 1 December 2009. It obliges the Union and its member states to "act jointly in a spirit of solidarity" if any member state is the target of a terrorist attack or the victim of a natural or man-made disaster.

Under Article 222, the Union is to mobilise all the instruments at its disposal, including military resources made available by member states, to:

• prevent the terrorist threat in the territory of member states;
• protect democratic institutions and the civilian population from any terrorist attack;
• assist a member state in its territory, at the request of its political authorities, in the event of a terrorist attack or disaster.

The clause is request-based: assistance is triggered by the political authorities of the affected state, distinguishing it from the separate mutual defence clause in Article 42(7) of the Treaty on European Union (TEU), which addresses armed aggression.

Implementation arrangements were established by Council Decision 2014/415/EU of 24 June 2014, which sets out how the clause is activated, coordinated through the Council, and supported by the Commission and the High Representative, drawing on instruments such as the EU Civil Protection Mechanism and the Integrated Political Crisis Response (IPCR) arrangements.

To date, Article 222 has not been formally invoked. After the November 2015 Paris attacks, France instead invoked Article 42(7) TEU, the mutual assistance clause, rather than the Solidarity Clause — a choice widely read as signalling that the response was framed as defence against armed aggression rather than civil protection cooperation.

The clause reflects the EU's evolution toward a security actor with internal crisis-response responsibilities, while preserving member-state primacy over how assistance is requested and delivered.