During joint operations in the Mediterranean, the European Border and Coast Guard agency (Frontex) has contributed to the implementation and development of the law of the sea. Under Frontex-led activities, frontline Member States such as Italy have encouraged an extensive interpretation of the United Nations Convention on the Law of the Sea provisions to extend the application of enforcement powers on the high seas. However, in an effort to intercept foreign ships suspected of having disembarked migrants on the Italian shores, border guard authorities started to intercept those ships directly on the high seas. Since these interception measures could have a significant impact on the freedom of navigation on the high seas, these practices should always find their legal basis in the key principles enshrined in the law of the sea and in other international law instruments.

Against this backdrop, this essay firstly focuses on the existing provisions regulating flag State jurisdiction, right of visit and right of hot pursuit in migrant smuggling operations on the high seas. Secondly, this analysis presents the evolution of the exercise of coastal State jurisdiction through the development of maritime interception practices adopted during Frontex operations. In the last part, accountability and responsibility during these maritime operations will also be discussed. The aim of this chapter is to present extensive legal approaches in the exercise of coastal States’ jurisdiction while highlighting a recent trend in using interception measures that could potentially affect the principle of exclusive flag State jurisdiction on the high seas.