To be fair, classic TOS was never spot-on and terribly well-defined at times concerning the purposes and missions of either the Federation or Starfleet. At times we were led to believe one was a defensive alliance a'la NATO while the other was purely scientific and exploratory in nature. Other times the UFP seemed like a unitary federal union or nation-state while Starfleet was its spaceborne army.
Forgive my two posts in a row. I still havent figured out how to multiquote from different people....
anyway, i agree with eddie. Thats the impression i was always left with TOS and Starfleet/The Federation.