Let's give two hearty cheers for the government of Japan, for coming into the open to present an important international policy question, and for the content of its message to the Brexit-challenged United Kingdom and European Union. The 15-page "Message" was published by the Foreign Ministry, but its main thrust is addressed to Theresa May's new government in London, which has pledged to follow through on the June referendum in which the people of the U.K. voted by 51.9 to 48.1 percent to leave the EU.

Prime Minister Shinzo Abe took up the question in his meeting with May on the sidelines of the summit of Group of 20 leaders in Hangzhou, China. He asked for May's help to keep Nissan and other major Japanese companies in the U.K. after Brexit finally happens. Japan's Foreign Ministry was on its best diplomatic behavior in summarizing the meeting of the prime ministers: "Prime Minister Abe requested her (May's) cooperation to enhance predictability and to continue to secure Japanese companies' businesses and value chains."

But the same Foreign Ministry officials broke normal mealy-mouthed bureaucratic cover in their message. British commentators described the document as "unprecedented." The message warns: "Japanese businesses with their European headquarters in the U.K. may decide to transfer their head-office function to continental Europe if EU laws cease to be applicable in the U.K. after its withdrawal." It noted that Japanese businesses in Europe have created 440,000 jobs, with the U.K. benefitting greatly. Last year nearly half of Japanese direct investment in the EU went to the U.K.