The pre-existing right to keep and bear arms was premised
on the commonplace assumption that individuals would use
them for these private purposes, in addition to whatever militia
service they would be obligated to perform for the state. The
premise that private arms would be used for self-defense accords
with Blackstone’s observation, which had influenced thinking
in the American colonies, that the people’s right to arms was
auxiliary to the natural right of self-preservation. See WILLIAM
BLACKSTONE, 1 COMMENTARIES *136, *139; see also Silveira,
328 F.3d at 583-85 (Kleinfeld, J.); Kasler v. Lockyer, 2 P.3d
581, 602 (Cal. 2000) (Brown, J., concurring). The right of self-
preservation, in turn, was understood as the right to defend
oneself against attacks by lawless individuals, or, if absolutely
necessary, to resist and throw off a tyrannical government. See
Silveira, 328 F.3d at 583-85 (Kleinfeld, J.); see also id. at 569-70
(Kozinski, J., dissenting from the denial of rehearing en
banc); Kasler, 2 P.3d at 605 (Brown, J., concurring).9
When we look at the Bill of Rights as a whole, the setting
of the Second Amendment reinforces its individual nature. The
Bill of Rights was almost entirely a declaration of individual
rights, and the Second Amendment’s inclusion therein strongly
indicates that it, too, was intended to protect personal liberty.
The collective right advocates ask us to imagine that the First
Congress situated a sui generis states’ right among a catalogue
of cherished individual liberties without comment. We believe
the canon of construction known as noscitur a sociis applies
here. Just as we would read an ambiguous statutory term in
light of its context, we should read any supposed ambiguities in
the Second Amendment in light of its context. Every other
provision of the Bill of Rights, excepting the Tenth, which
speaks explicitly about the allocation of governmental power,
protects rights enjoyed by citizens in their individual capacity.
The Second Amendment would be an inexplicable aberration if
it were not read to protect individual rights as well.
Parker v. District of Columbia
http://pacer.cadc.uscourts.gov/docs/common...03/04-7041a.pdf
A masterfully written opinion, I recommend you read it in its entirety.