This course is about the makeup and breakdown of the law of the sea treaty regime.In September 2013, the United States, a non-signatory of the UN Convention on Law of the Sea, signed the latest in a number of maritime boundary conventions, this time with Kiribati. And in March 2014, China, a signatory of the Convention, deflected a Filipino submission to the Permanent Court of Arbitration over claims to parts of the South China Sea. These not atypical developments suggest that the modern law of the sea regime — put into place by three conferences held in 1958, 1960, and 1973-1982 — may not be as necessary, or as effective, as its proponents had once believed. Codifying the law of the sea was a hugely ambitious project, pushing at sovereignty’s last frontier before outer space. First, it aimed to absorb customary law on the territorial sea, the continental shelf, the high seas, and fishing, into a treaty regime. Second, it articulated new international law concepts such as ‘exclusive economic zone’, ‘archipelagic state’, and transit passage through international straits. And finally, it offered a range of options for dispute resolution, which, provided states did not opt out of the regime, demanded that once a decision was handed down, states were bound to abide by them. Two issues have dominated the development of the regime: international security and the exploitation of resources. The powerful maritime states have sought the right of innocent passage through territorial waters and EEZs, and pushed for rights when traversing the high seas, archipelagos and straits. At the same time, the coastal states have laid claim to expanded territorial waters, contiguous zones, exclusive economic zones, and greater control over the resources within them. The concerns over security and resources have touched every component of the Convention, from the protection of the marine environment, to the conduct of scientific research. Some tensions have not been resolved, and the coming period may see the fraying, if not the unravelling, of the current arrangements.