Information about Japanese who give up Japanese citizenship

But there is someone there whose Japanese wife had US citizenship and recently ran away with their child in Japan. Im assuming, but dont know for sure, that she did this post-1985. He is trying to get the Japan courts to apply US law since she is a US citizen. But the US embassy advised him that Japan would likely do whatever necessary to give her the advantage. It will be interesting to see how this turns out later next year. 

UPDATE: He has been successful in getting his wife's Japanese citizenship revoked. In fact, the Ministry of Justice was willing to write a letter to that effect.  But his child retained Japanese citizenship, so the courts are using this as a reason to apply a certain amount of Japanese law.  Even in the areas where they have agreed to apply US law of the appropriate state, they are no doing so at all, in a fairly blatant way.  When this is over, we may have some good documents available on how Japanese courts say one thing about applying Japanese law, and do another.

Need more information on the process required to get the Ministry of Justice to revoke citizenship.

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