Initially defined US v Miller, and then broadened in Heller.Yes, District of Columbia vs. Heller did define the right to possess a firearm for "traditionally lawful purposes" such as self-defense within the home.
But to claim the argument was roundly rejected by the Supreme Court in a 5/4 decision is bullshit.
Held:
1. (d) The Second Amendment s drafting history, while of dubious interpretive worth, reveals three state Second Amendment proposals that unequivocally referred to an individual right to bear arms. Pp. 3032.
That is basing the decision on a small minority of the 13 states.
Plus, District of Columbia vs. Heller held things you right wing turds don't want to hear:
2. Like most rights, the Second Amendment right is not unlimited. It is not a right to keep and carry any weapon whatsoever in any manner whatsoever and for whatever purpose: For example, concealed weapons prohibitions have been upheld under the Amendment or state analogues. The Courts opinion should not be taken to cast doubt on longstanding prohibitions on the possession of firearms by felons and the mentally ill, or laws forbidding the carrying of firearms in sensitive places such as schools and government buildings, or laws imposing conditions and qualifications on the commercial sale of arms. Millers holding that the sorts of weapons protected are those in common use at the time finds support in the historical tradition of prohibiting the carrying of dangerous and unusual weapons. Pp. 5456.
Miller vs. U.S. defined what firearms are protected under the second amendment.
Under Miller, flintlocks are not protected by the 2nd.
Weapons in common use of the time