Its action is being brought under the United Nations Convention on the Law of the Sea and the Ospar Convention on the Marine Environment.

BBC: Irish start legal action over Sellafield

According to the United Nations Convention on the Law of the Sea, countries are entitled to exclusive economic zones up to 200 miles from their shores.

CNN: Countries in tug-of-war over Arctic resources

This seems based on a 1940s map giving China virtually the whole sea, ignoring the 1982 United Nations Convention on the Law of the Sea (UNCLOS).

ECONOMIST: The South China Sea becomes a zone of eternal dispute