On again - off again tensions between China and Japan are apparently on again.
The islands off the northeast coast of Taiwan, known as Senkaku in Japanese and Diaoyutai or Tiaoyutai in Chinese (depending on which Romanization system you prefer) has been administered and controlled by Japan since 1895 except for the post-WWII period to 1972 when they were administered by the United States in accordance with the Peace Treaty of San Francisco under rights granted by the United States to administer and dispose of any lands not covered by the peace treaty.
There have been several instances in the past few decades where Chinese or Taiwanese fishing vessels would be passing through the territorial waters of the islands would be stopped by Japanese authorities and their captains arrested. This, as has been reported in the news, has dominated headlines in this part of the world for the past week.
China has little legal reason for a claim of these islands, while Taiwan's claim is very strong, deriving from a Tokyo court decision in the 1930s ruling that those islands were part of Taiwan governed from the Japanese prefectural government in Taipei rather than from Tokyo or Naha (in Okinawa). As such, those islands would have been renounced along with the main island of Taiwan itself in accordance with the terms of the Peace Treaty of San Francisco.
As China has never administered or governed those islands, and as China is not party to any treaty by which it is granted sovereignty or administrative rights to those islands, it has no legal claim to them. Of course, they know this and are not eager to have the International Court of Justice (this falls within the ICJ's jurisduction) ajudicate this, nor are they willing to allow the Taiwan matter to see the halls of the court either, because they know they would lose.
There is also a significant dispute regarding EEZ in the East China Sea. China claims an absurd EEZ line that runs up nearly all the way to the southern Japanese Ryukyu Island Chain (not part of the Senkaku/Diaoyutai) island dispute while Japan claims the median line between the two baselines of the respective countries.
China is now suspending talks with Japan regarding disputes in the East China Sea as a result of the continued detention of the captain of the Chinese boat who went into what Japan regards as its sovereign waters around the Senkaku/Diaoyutai islands...