Emanuele Agosti
The principle that an attack on one is an attack on all is not, as the common debate suggests, an exclusively Nato principle. Rather, it is a duty contained in all mutual defence clauses, implemented through various legal obligations and procedures. This paper examines Article 42(7) TEU, a provision of particular interest due to its potential role in shaping the evolving European security architecture. Notably, it features an unusually broad casus foederis, operates on a horizontal, reciprocal, and intergovernmental basis, and shares an overlapping scope with two other mutual assistance clauses - Article 222 TFEU and Article 5 of the North Atlantic Treaty. The interactions among these provisions are analysed from multiple perspectives. The paper also draws from past experiences and explores realms of future applicability.
