In March 2009, a group of citizens filed a lawsuit demanding that the state disclose three diplomatic documents related to the 1972 reversion of Okinawa from U.S. to Japanese rule. The government had turned down a September 2008 request based on the Freedom Information Law to disclose the documents saying that there was no evidence that the documents exist or that they had been destroyed or transferred. But the United States already disclosed the documents in 2000 and 2002.

The documents concern Tokyo's financial concessions to Washington over Okinawa's reversion: $200 million mainly for the transfer of U.S. military bases, $65 million for maintaining and improving the conditions of U.S. military bases and secret payments making up $4 million in costs to convert U.S. military areas back to farmland.

Mr. Takichi Nishiyama, an ex-Mainichi Shimbun reporter who had obtained a photocopy of the document linked to the secret $4 million payments, is among the plaintiffs. He had been convicted of violating the National Public Service Law for persuading a Foreign Ministry worker to bring him classified information.