I'd say the Second Amendment is a Civil Liberty.
The Right to Keep and Bear Arms is a "God given" right, pre-existing any government.
The Second Amendment is a Civil Liberty, protecting people from a government that might try to infringe on that pre-existing right in the vein of the Locke "social contract".
In that contract we the people give the government permission to act on our behalf. Violate that contract and we may remove said government from power any time we wish.
Liberty being as John Stuart Mill defined it: freedom to act, absence of coercion.
Right, a legal or moral entitlement. In the case of RKBA, recognized by the founders as an entitlement, given by God to man to defend life and freedom.
It's pretty heavy stuff which is why so many anti's can't grasp the concept. They can't grasp the concept, as our founders DID, that "we the people" should always have the ability to pick up our shotguns, "assault weapons", .50 caliber "sniper rifles" with our "cop killer bullets" and remove, by force if necessary, a government gone out of control. It is that always present possibility, our founders believed, that would keep government from going out of control in the first place. It is still a valid concept, and Scalia's writings in Heller talk about it being still valid.
That's a scary concept, maybe not even practical, but it is core belief on which the Constitution was founded, that the people wield absolute power and the only way to keep it that way is for us to be able to fight back if necessary.