That would presuppose that the Members governments and peoples are subordinate to the Federation Council. As oppose to the Members being sovereign entities that have agreed to form a subordinate interstellar body with a limited number of duties and powers. The Federation as Kirk described it in Spectrum of the Gun.
And then there's Daniels' description of the UFP in the 26th century ... which is the same as Kirk's description of the UFP in the 23rd.
More likely thanks to Archer... But I think it's more a case of the future never being written in stone.
I don't think we have a canonical answer to this, but we've seen a couple of non-canonical options in the novels: - Captain's Peril (2002) by William Shatner and Judith & Garfield Reeves-Stevens used the Uniform Code of Starfleet Justice, as you suggested above. - Destiny Book I: Gods of Night (2008) by David Mack went with Starfleet Code of Military Justice. I'd probably tend to go with SCMJ myself, since a) it sounds better, and b) it was from Destiny, and Destiny = awesome.
So if Colonel West was a "Marine" and there is a "Marine Corp" (Starmaines?) then they would have a separate code of military justice? Which would be fine, we basically had that for over half of the history of the United States. And what about the Federation maritime patrol? And if the Member do maintain their own "home fleets" what about them. If we aren't employing unified, and we are stipulating Starfleet. So how would that have work in a situation like the one where Deanna Troi ordered (holographic) LaForge into a radioactive chamber in order to effect a critical repair, the entire ship's company is under the charge of the medical department. Sometimes people are going to be harmed on assignment, and sometimes knowingly sent to their deaths. Doctor: "Captain I'm afraid I can't allow you to take the ship into combat, someone might be injured."
Well, I think the name I've seen for this postulated marine corp is "Starfleet Marine Corps", so they'd fit under the SCMJ without any problems! I don't know much about them, but it sounds possible that they are a Federation civilian agency? At any rate, since they're not Starfleet, they presumably wouldn't fall under the code, since either version has "Starfleet" in the title. I would assume that each member world would have their own justice code that would cover their home fleets. I'm guessing the intent was a much narrower definition of "under their medical charge" than what you've written here. Presumably it would refer to people actually receiving medical care at the time?
^ Works for me, with the exception that I believe organizationally the Marines would be separate from the Fleet.
In Enterprise the MAKOs were seperate and had to be authorized access. On TOS we only saw Starfleet security. In TMP we saw Perez in the "football" armor, which we could assume meant he was a marine, although in ST3, Sulu called them "agents." "Side elevator, agents on their way up...don't call me tiny." Again in TNG we only saw 'fleet security. Starfleet vessels, for all of their military responsibilities, are still exploratory and diplomatic vessels, and Marines would be purely military. CCC.
We did see a few people in different style uniforms during the short war with the Klingons in DS9. But I don't recall what they were.