Article 2 of UNCLOS (United Nations Convention on the Law of the Sea) defines maritime sovereignty of a Coastal State beyond any doubt, to extend beyond its land territory to the territorial sea, which Article 3 identifies broadly as the 12-mile limit. The purpose of the territorial sea naturally is to ensure that the State can implement and enforce its laws, in the protection of its people, by addressing key priorities, including health and safety, immigration, defence and terrorism, marine and agricultural environmental protection, revenue and resource protection. UNCLOS provides a strong check on unlimited management control by Port State on ships engaged in innocent passage through territorial seas. Article 27 states that the criminal jurisdiction of the Coastal State should not be exercised on board the ship of another Flag State passing through its territorial sea to arrest any person or to conduct any investigation in connection with any crime committed on board the ship during its passage, save only if the consequences of the crime extend to the Coastal State; or if the crime may disturb the peace of the country or the good order of the territorial sea; or if it is necessary to do so in order to control illegal drug trafficking; or, if the Master (or a diplomatic officer or agent of the Flag State) specifically asks the Coastal State to assist. In any such circumstances in which the Coastal State seeks to exercise its criminal jurisdiction on the vessel, if the Master so requests the Coastal State must notify Flag State.