Legal background International law: the United Nations Convention on the Law of the Sea, the United Nations Fish Stocks Agreement and Regional Fishery Management Organisations UNFSA
UNFSA is a multilateral treaty intended to ensure the long-term conservation and sustainable use of straddling fish stocks (stocks which migrate between, or occur in both, the EEZ of one or more States and the high seas such as mackerel, herring and whiting) and highly migratory fish stocks (stocks listed in Annex 1 of UNCLOS which are capable of migrating long distances and which generally occur in both EEZs and the high seas) through effective implementation of the relevant provisions of UNCLOS (UNFSA, Article 2). In order to achieve this objective, UNFSA sets out various principles for the conservation and management of these stocks by the coastal state within its EEZ, and by the coastal State and other states on the high seas. The UK is currently a party to UNFSA in its own right.
	Part III of UNFSA contains detailed provisions on the implementation of Articles 117 to 120 of UNCLOS. This includes provision on the establishment and functions of RFMOs and duties of States to cooperate with them (Articles 8-17). In particular, States fishing for stocks managed by a particular RFMO on the high seas and the relevant coastal States must either join that RFMO or agree to apply the conservation and management measures adopted by the RMFO (Article 8(3)). UNFSA also imposes duties on States to implement and enforce conservation and management measured adopted by RFMOs.