General international law in the preamble of the United Nations Convention on the Law of the Sea: origin, identification, and application

Since the adoption of the United Nations Convention on the Law of the Sea (UNCLOS), maritime disputes and issues have continuously emerged worldwide. All coastal States face serious challenges in the law of the sea, such as maritime delimitation, maritime rights distribution, and maritime law enforcement. To defend their maritime rights and interests, coastal States should make good use of the rules of UNCLOS. Although the substantive provisions of UNCLOS can play an important role in resolving maritime disputes, UNCLOS, as a package agreement, does not exhaust all matters related to maritime rights and obligations. Indeed, not all legal issues involving the ocean are governed by UNCLOS. When facing key issues such as historical rights, it is not sufficient to rely solely on the provisions of UNCLOS. It is also necessary to refer to general international law mentioned in the preamble of UNCLOS and use it as applicable legal arguments. This paper argues that ‘general international law’ contained in the preamble of UNCLOS cannot be regarded only as ‘customary international law’ and it is an evolving collective concept that can be applied to fill gaps in UNCLOS and ensure its completeness, which could be proved through positions and practices of different States or decisions and judgments of different international judicial and arbitration bodies relating to maritime disputes.