I'm not implying that China owns all the sea territories they claim they own nor siding with any countries. I've just found that articles in the media can be a bit misleading at times. The map here shows Brunei, Malaysia, Philippines and Vietnam's exclusive economic zone according UNCLOS and what Chinese/Taiwanese claim but what about China/Taiwan's economic zone according to UNCLOS? I did a search and couldn't find there's a map by the UN showing every nation's economic zone. I did find United Nations Convention on the Law of the Sea of 10 December 1982 (http://www.un.org/depts/los/convention_agreements/texts/unclos/UNCLOS-TOC.htm
). So my understanding is UN does have laws for nations to use to claim their sea territories. And if two nations claim to own the same island then there will be a dispute and it's up to the involving nations to resolve it and if they cannot they might take it to the International court. Correct me if I'm wrong.
In terms of how far the islands are from a nation that claims it, I don't think distance is enough to reject a nation's claim. Hawaii is nowhere near USA's mainland but no one doubts why they own it. Britain, France and maybe some other nations used to and I guess probably still own some islands that are far away from their mainlands.
The other thing I wonder is whether countries like USA should have much to say regarding UNCLOS issues since they haven't signed yet.