The issue of this dissertation is what measures Norway, as a port and coastal State, has to regulate the exchange of ballast water by foreign vessels in its coastal areas for the prevention of introduction of alien invasive species, which constitute a threat to the marine biological diversity. On 1 July 2010 Norway’s Ballast Water Management Regulation entered into force. The Regulation, which is enacted in accordance with the Ship Safety and Security Act and the Nature Diversity Act, is the result of Norway acting upon its international obligations, namely the International Convention for the Control and Management of Ships’ Ballast Water and Sediments to which Norway is as a signatory power. The main focus of this dissertation is the BWC’s rules on ballast water exchange. These rules are necessarily aimed at the vessels carrying the ballast water, which is under the jurisdiction of its flag State. An interesting problem that arises is therefore what measures Norway, as a port and coastal State, has according to international law to regulate and ensure that the BWC’s rules on ballast water exchange are abided by.