I found the information about the regulations governing tour guides that I mentioned earlier. It's on the website of the Ministry of Barrels, Pork, and Boondoggles:

Licensed tour guides - "Individuals who want to accompany foreigners and provide them with travel guide services using a foreign language for remuneration have to pass an examination given by the JTA Commissioner and acquire a license issued by a prefectural government. "

http://www.mlit.go.jp/kankocho/en/sh...i/tsuyaku.html

The page has a link to a search tool that lets you search for licensed guides in each region of Japan.