I am pretty sure it is entirely legal to refer to oneself as doctor if you claim to be an expert in herbal medicine or gravity treatments or some such quackery. You would get into serious trouble if you tried to append MD to your name. We are pretty picky on that point.
T. MD.
You sign yourself as "MD" which I take to mean that you're a graduate of a medical school.Assuming further that you're licensed to practice medicine somewhere in the US would you still be allowed to bill yourself as "MD" if your license were to expire,be suspended or be revoked? I obviously understand that you wouldn't be allowed to *practice* medicine in any such situation.