Contiguous Zones in the Gulf of Finland
On 23 January 2023, it was reported that Estonia was planning to establish a contiguous zone (CZ) in the Gulf of Finland. While the creation of a CZ off the coast of Estonia would not, as was quickly claimed, cut Russia off from the Baltic Sea, even if also Finland were to create a CZ. But the proposed measures are not meaningless and have the potential to affect Russian naval operations in the Gulf of Finland, at least if Finland, too, were to establish a CZ and use the legal options available to coastal states in a proactive manner. Declaring a CZ can contribute to the national security of the coastal state by introducing the reader to the rights and obligations of coastal states and flag states in a CZ, in particular when compared to the territorial sea or the high seas. Currently, Finland only has 2 nautical mile customs zone beyond the territorial sea (Koivurova et al. (2019). The Baltic Sea and the Law of the Sea - Finnish Perspectives, Zürich: Lit Verlag, pp. 30 et seq.). It would make sense for Finland to expand its existing CZ in both geographical and material scope.
The legal basis for the creation of a contiguous zone is found in Article 33 of the United Nations Convention on the Law of the Sea. The norm reads as follows:
“1. In a zone contiguous to its territorial sea, described as the contiguous zone, the coastal State may exercise the control necessary to: (a) prevent infringement of its customs, fiscal, immigration or sanitary law within its territory or territorial sea, (b) punish infringement of the above laws and regulations committed within its territory or territorial sea.
2. The contiguous zone may not extend beyond 24 nautical miles from the baselines from which the breadth of the territorial sea is measured.”
The CZ is part of the Exclusive Economic Zone, if one has been declared by the coastal state - otherwise, it is part of the High Seas. The declaration of a CZ by the coastal state generates additional rights for the coastal state but it does not alter the legal status of the waters in question otherwise.
Article 33 (1) (a) UNCLOS means that the coastal state can prevent violations of its laws by incoming ships, Article 33 (1) (b) UNCLOS allows punishing violations by outgoing ships (this is explained eloquently in more detail by Copenhagen-based legal scholar Yoshifumi Tanaka in his textbook “The International Law of the Sea”, 3rd ed., Cambridge: Cambridge University Press, p. 147). The norm does not provide the coastal state with a particular power to legislate separately in the CZ, but it allows law enforcement beyond the territory of the state for violations of the law that have happened in the territory (usually internal waters or territorial sea). If needed, Article 111 UNCLOS allows the coastal State to engage in hot pursuit, following an offending vessel beyond the CZ.
The material scope of the laws that can be enforced in the CZ is limited. National security is not mentioned expressis verbis, but the enforcement activities permitted under Article 33 UNCLOS allow for increased maritime domain awareness. Currently, Finland only uses its CZ for customs purposes, and it has not yet made use of the maximum geographical scope of Article 33 UNCLOS. There has been some discussion in the past about possibilities for coastal states to claim CZ powers in excess of the rights contained in UNCLOS, but it appears that UNCLOS also reflects the existing customary international law.
But that does not mean that CZ operations would not contribute to national security. Were both Finland and Estonia to establish CZs in the Gulf of Finland to the maximum extent possible under UNCLOS both with regard to the geographical material scope, they could, together, increase maritime domain awareness significantly. Doing so would not prevent passage through the CZs by foreign ships - because the legal status of these waters would not change with regard to vessels flying the flags of third countries. But doing so would provide a bit more options to enhance safety and security in both countries and at sea. The creation of an expanded CZ in line with UNCLOS would be a simple measure that would be compatible with the international law of the sea and as such could not be considered provocative as the rights of other states would not be affected.