I’m not sure that they’ve ever addressed this in depth, but I’ve always wondered about it. Is the Federation a sovereign state in and of itself, or is it something akin to the European Union in which all the member states (or in this case planets) are sovereign entities but operate under a basic set of laws and principles, share a common currency and have open borders with each other. Or is it something else altogether, like for example where the Federation is the supreme governing body, but all the planets are semi-autonomous entities with a good degree of latitude on setting domestic policy?
I had my own answer, but I think Memory Alpha states it perfectly:
The United Federation of Planets (abbreviated as UFP and commonly referred to as the Federation) was an interstellar federal republic, composed of planetary governments that agreed to exist semi-autonomously under a single central government based on the principles of universal liberty, rights, and equality, and to share their knowledge and resources in peaceful cooperation and space exploration
For more information, try the full article.
ETA: I’ll add my bit: Every time the people of the Enterprise set foot on a planet, they are required to follow the laws of that planet. Following local law is really important. This is what led me to choose option 3 above. However, the Federation is sovereign in that your laws cannot violate their basic principles. And you let the Federation handle interstate trade. It’s pretty analogous to the United States, at least as originally designed.
Oh, and they do have a military arm, Starfleet, which also makes them different than the EU.
I always assumed the Federation was equivalent to the US, with Earth as DC
A bit stronger than the U.N., a bit less pervasive than the modern U.S. model. Think of the popular conception of sovereignty in the days when “The United States are…” was good grammar* for a good parallel.
- Note that I’m not suggesting that conception was accurate in terms of U.S. political theory, only that it provides a good analogy to the actual dvision of sovereignty under the U.F.P., at least in the T.O.S. period, insofar as the storylines presumed a consistent background polity.
The use of money was in the Federation was highly illogical. In the original series, there were credits, in Star Trek IV, Kirk is confused when he finds out that money is still used. Ther are several episodes in TNG where it’s stated the the notion of money had been abandoned. They also used money to buy money from the Ferengi.
The Federation also issues Passports. At least, I picked one up at a convention a few years back. Not sure if I could actually use it for interstellar travel, though.