Disputed natural gas reserves beneath the East China Sea are once again making headlines, as China and Japan spar over which of the two countries has the rights to the underwater reserves.That became clear last week when Japanese Foreign Minister Katsuya Okada warned his Chinese counterpart Yang Jiechi that Tokyo will take "certain" action if Beijing violates a bilateral accord to jointly explore for gas in the East China Sea.In particular, Okada told Yang that Tokyo will take countermeasures if Beijing begins gas production in the Chunxiao gas field, arguing that his country would consider such action a violation of a 2008 agreement to jointly explore the area.It's worth observ...