starfleet is NOT the military. starfleet's primary missions are exploration, diplomacy and has secondary roles of humanitarian relief and defense not because it's made for those but simply it already has the hardware flying through out the galaxy with the infrastructure like all the star bases so might as well plaster a phaser or two on them just in case when they are out exploring shit hits the fan.
some points to consider:
-captain jean-luc f***ing picard said himself starfleet was NOT military, pretty sure he knows what he is talking about, the idea he was sharing his opinion is pure rubbish. Go join the army and start walking around telling everyone "THE ARMY IS NOT A MILITARY!!"
-people keep their same positions for 30 years (TOS crew).. in a military this does not happen - though it does happen in the civilian science world, go figure
-oddly enough officers in starfleet outnumber enlisted a seemingly 100-1, in a military this does not happen
-whole ship is designed for science and diplomacy - look how many windows is on and how cushy the enterprise-d is... strange for a "military" ship to look like a carnival cruise ship in space packed full of 5 star rooms and science labs and families and dolphins with only one forward torpedo launcher and a couple phaser strips... thats like the uss arizona having a lone 5 incher squeezed between a superstructure of luxury oceanside balcony suites
-sisko makes a huge deal about the defiant being starfleets first ship designed for war... not building a warship for its first 200 years of existence does not happen in a military
-archer had to call in help (or admiral called it in for him, i forget) the military.... kinda paradoxical for the military to be freaked out by an enemy they cant fight so they call in "the military"
- adm marcus starts building a military for what many claim is the "military"... again rather paradoxical
-court martial thing, well we're five years out from earth, i guess subspace mail the police a report (not)... i think it just makes sense for any organization flying around in deep space to have their own legal system
-military dont recruit handicap people for obvious reasons (one whack by a klingon batleth and there goes your VISOR flying, youre kinda worthless now fighting, the primary mission of a military is to fight probably going to want people who dont have physical handicaps that prevent them from doing so).... geordi and bashir's girlfriend shouldnt be in starfleet
-military ranks and organization, well go join a crew of a merchant ship (have to get licensed first) and youll be surprised to find military ranks and military structure - why? because in a ship environment that kind of organization is what works best. so if having a military nautical organizational structure makes starfleet military, then the exxon valdez was military too along with all the container and tanker and whatever else in the world
my personal opinion is starfleet is like a massive space faring version of the NOAA Corps
http://en.wikipedia.org/wiki/National_Oceanic_and_Atmospheric_Administration_Commissioned_Corps
liie with the merchant marine there could be some sort of reserve military authorization clause that can transform starfleet into a military during a crisis like during the klingon cold war in the tos movies (could explain the sudden change in uniforms and atmosphere we saw in Wok through TUC) or during the timeline in yesterday's enterprise were starfleet was pretty much explicit stated it was a military. but in peace times the merchant marine reverts to being civilian, i think the same happens to starfleet.
but in its normal times starfleet is not a military
KDF Roms, and the cardies on the other hand have outright militaries and its pretty explicit in the show that they are militaries theres no question