Guy Gardener wrote:
Vulcans vs. Romulans = Non Interference Policy = A strictly internal matter.
Starfleet, and all Vulcans in Star Fleet have to take a step back from any Romulan occupation of Vulcan.
Vulcan would have to withdraw from the Federation, or most to all of the Vulcan's in Starfleet would have to resign their Starfleet Commissions which would drastically weaken the Federation, opening the Neutral Zone like a flower licked by the first drip of morning sunlight.
This loophole would not come into effect until the Romulan ships made landfall and there were boots on the ground.
That's not a strictly internal matter, that's a Federation world being attacked by a non-Federation world. And even if the Romulans can point to that in the charter and say "See, you have to leave us alone!" I'm pretty sure they'd be willing to violate the prime directive to stop their mortal enemy from having a military foothold right next to Earth.
If the Federation can't even protect its own planets from outside invaders, being a Federation member is about as useful as being a UN member.