People in and of Taiwan (such as me) have paid attention to international law, about when sovereignty is transfered--or lost (as you suggest). The significance is clear regarding legal status of Taiwan. For the same reason, it is important to resolve that of Senkaku islands. Precise because international law is on Japan's side with respect to sovereignty of Senkaku islands, US Secretary of State proposed this yesterday at Hanoi.
Chen Lung-chu 陳隆志, Taiwan's statehood is undeniable. Taipei Times, Aug. 17, 2007.
http://www.taipeitimes.com/News/editorials/archives/2007/08/17/2003374626
The summary of my argument is whatever Mr. Ma Ying-jeou might have said around 1970, Senkaku islands are Japan's, simply because it (cabinet, to be exact) declared sovereignty over the islands in 1895. The apt analogy is when an explorer reach an uncharted territory during
Age of Discovery
http://en.wikipedia.org/wiki/Age_of_Discovery
, the first thing he would do was to plant a flag and proclaim ownership on behalf of the crown. That is how sovereignty is created and how international law is developed. It did not matter that there were aboriginals already living there. (President Chen Shui-bian, while in office, advocated
Popular sovereignty
http://en.wikipedia.org/wiki/Popular_sovereignty
, but I have not delved into it.