Coastal state jurisdiction is the jurisdiction enjoyed by the coastal state in relation to breaches of regulations and laws by foreign flagged ships that take place within its jurisdictional zones. The prescriptive and enforcement jurisdiction comprise the main jurisdictions of a coastal state. Prescriptive is the jurisdiction to prescribe laws and regulations and Enforcement is the jurisdiction to enforce such laws.

The Customary International Law is one of the main sources of International Law, involving the principle of custom. The International Court of Justice Statute defines customary international law in Article 38(1)(b) as "evidence of a general practice accepted as law". This is generally determined through two factors: Firstly, the general practice of states (the objective element) and secondly, the opinion juris i.e. what states have accepted as law (subjective element).

The North Sea Continental Shelf Cases confirmed that both State practice (the objective element) and opinio juris (the subjective element), are essential pre-requisites for the formation of a customary law rule.

It is noticeable to say that article 1(4) of the United Nations Convention on the Law of the sea (UNCLOS) defines what the pollution of marine environment is. Also, article 237 Unclos includes specific provisions on the relationship between UNCLOS and other conventions on the protection and preservation of the marine environment. Thus, the obligations under other conventions regarding the prescriptive and enforcement jurisdiction of a coastal state, are without prejudice the UNCLOS' provisions, however they should be carried out in a manner consistent with the general principles and objectives of the UNCLOS Convention.

High seas

a) Prescriptive rights

There is limited jurisdiction by the coastal state on the high seas under customary international law and UNCLOS. The basic regime is exclusive flag state jurisdiction as per articles 91, 92 and 94. Therefore, Flag state jurisdiction is that exercised by the flag state. Coastal states do not have prescriptive rights for foreign flag ships. Every state can sail ships flying its flag (Art 92), however, every state shall fix the conditions for the grant of its nationality to ships, for the registration of ships in its territory, and for the right to fly its flag (Art 91). Ships have the nationality of the State, whose flag they are entitled to fly. Thus, there must exist a genuine link between State and the ship.

Article 86 defines the area within the provisions of high sea apply, where the Exclusive Economic Zone (EEZ), territorial sea, internal waters and archipelagic waters are excluded. Therefore, the high sea is beyond the jurisdiction of a coastal state. According to article 87, the high seas are open to all states, and the freedom of high seas is exercised under the provisions of UNCLOS and by other rules of International law. The prescriptive jurisdiction can be seen in articles 211(1-2) and 212. Article 211(1-2) refers that states shall establish compulsory international rules and standards through competent International organizations, such the IMO, to prevent, reduce and control pollution of marine environment from vessels flying their flag or of their registry. Article 212 says that states shall adopt laws and regulations to prevent, reduce and control pollution of the marine environment from or through the atmosphere. In addition, one can argue that the flag state according to article 94(3), has prescriptive jurisdiction, ensuring the safety at sea. Last but not least, States have the right to take and enforce measures (both prescriptive and enforcement rights) beyond their jurisdictional zones in order to protect their coastline or related interests from pollution or the threat of pollution arising from maritime casualties.

b) Enforcement rights

Within the high seas the coastal state enjoys no specific rights of maritime regulations and enforcement other than the continuing right of hot pursuit under that sui generis regime, and the capacity to intervene in the case of a maritime disaster of the coastal state, including fishing (Art 221).

According to article 92(1), the flag state has exclusive enforcement jurisdiction on ships (sailing under its flag) on a hisgh seas. It is jurisdiction enforceable anywhere in the world and is practically limited by the capacity of a state to board and inspect ships which may be anywhere around the world. A flag state effectively exercises its jurisdiction and control administrative, technical and social matters over the ships flying its flag as per article 94, which expresses the duties of the flag state. Article 97, refers to the penal enforcement jurisdiction a flag state has in matters of collision or any other incident of navigation. Also, one can argue that the flag state according to article 94(3), has enforcement jurisdiction, ensuring the safety at sea. In addition article 217 (enforcement by the flag state) mentions that states need to ensure compliance by vessels flying their flag or their registry with applicable international rules and standards established by the competent international organization (IMO) or general diplomatic conference, and with their laws and regulations adopted in accordance with UNCLOS. Thus, states can inspect and detain/ restrict vessels from sailing, provide immediate investigation for particular breaches, institute proceedings and ensure sufficiently high fines in case of breaches.

Last but not least Article 218(1) refers to the enforcement right by port state. Non-flag port states are empowered to investigate and take proceedings (enforcement rights) against vessels voluntarily within their port, in respect of any discharge by such vessel beyond their jurisdictional zones in violation of applicable international rules and standards.

c) Customary International Law

Overall, there is limited jurisdiction by the coastal state on the high seas under customary international law and UNCLOS. The basic regime is exclusive flag state jurisdiction as per Art 94. Coastal states do not have prescriptive rights for foreign flag ships. Nor do they have enforcement rights except in particular circumstances (e.g. art 110(2) ).

The most important authority, regarding the high sea is the Lotus case, which established two (2) principles. The first principle mentions that a state cannot exercise its jurisdiction in any form outside its territory unless an international treaty or customary law permits it to do so (para. 45). This is what is called the first principle of the Lotus Case. The second principle states that within its territory, a state may exercise its jurisdiction, in any matter, even if there is no specific rule of international law permitting it to do so (paras 46-47). In these instances, the states have a wide measure of discretion, which is only limited by the prohibitive rules of international law.

In the New Zealand case held, that it was an essential feature of the freedom of the high seas and the freedom of navigation that the state of nationality of a ship (the flag state) had exclusive jurisdiction over the ship when it was on the high seas. In addition, under the rules of international law a port state had no general power to unilaterally impose its own requirements on foreign ships relating to their construction, their safety and other equipment and their crewing if the requirements were to have effect on the high seas. Any requirements could not go beyond those generally accepted, especially in the maritime conventions and regulations.

In addition, customary international law can be seen in the High seas Convention 1958, in the 1958 Geneva Conventions on the Law of the Sea and in 1969 International Convention relating to Intervention on the High seas in case of oil pollution Casualties.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.