The East China Sea has been described by someexperts as a potential “flashpoint” of interstate conflictand great-power rivalry and a source of regionaldestabilization.1 Much attention has focused onmilitary activities in this maritime theater, primarilyinvolving Japan, China, and South Korea. In contrast,this essay focuses on the complex maritime andsovereignty claims of Northeast Asian states in the EastChina Sea and unpacks the differing legal principlesthey use to support their claims in order to understandthe enduring nature of the conflicts. These disputesare challenging precisely because they involve contestsover both territorial sovereignty and maritime rights.The presence of different legal principles that statescan draw on to defend their national interests makesthese disputes more intractable, as states inconsistentlyuse international legal principles to maximize theirmaritime entitlements.