MPERIAL ROME: Did a Centurion surrender his sword when he retired from the Army and was granted a landholding in conquered territory? (Actually, I have no idea ... but letting him keep it might not be a terrible idea.)
I have no idea if a centurion kept his sword when he retired, but ITTR weapons inside Rome were forbiden for anyone except the vigiles, so even if he had it, he could not bear it inside the city.
And, after all, are current soldiers allowed to keep their guns when they are discharged?
It could also be the result of the 57th Century Bill of Rights granting every citizen the right to bear arms for personal defence.
IMHO this would be determined by the Law Level of the system you're at, but the local security would be seen as a matter for the local forces (be them from local nobles, governments or whatever), not for armed civilians, ther former military status notwithsanding.
In resume, again IMHO, you can be given a weapon (probably not a suport one, though), but being able to bear it (not to say to use it) or not would depend on the LL of wherever you are at each moment. If you have a Starship, you can have it there, but if you're travelling as pasenger, you may have problems to have it when you're on a planet (unless there's some place in the starport to store it while on planet).
Of course, YMMV