What mistake do I think you are making? You said: "It actually refers to the government's legal authority to mandate that privately owned businesses provide separate nut equal facilities for blacks". No law ever forced private businesses to serve blacks in the south until the civil rights act. They may have been forced to racially segregate, but no law every forced white southern business owners to serve blacks.
http://en.wikipedia.org/wiki/The_Negro_Motorist_Green_Book
What mistake do I think you are making? You said: "It actually refers to the government's legal authority to mandate that privately owned businesses provide separate nut equal facilities for blacks". No law ever forced private businesses to serve blacks in the south until the civil rights act. They may have been forced to racially segregate, but no law every forced white southern business owners to serve blacks.