A View of the Constitution, by William Rawle, 2 Ed., 1829, Chapter 10: "Of the Restrictions on the Powers of Congress - and on the Executive and Judicial Authorities - Restrictions on the Powers of States, and Security to the Rights of Individuals"
The preceding article expressly refers to the powers of congress alone, but some of those which follow are to be more generally construed, and considered as applying to the state legislatures as well as that of the Union. The important principles contained in them are now incorporated by adoption into the instrument itself; they form parts of the declared rights of the people, of which neither the state powers nor those of the Union can ever deprive them.
A subsequent article declares, that the powers not delegated to congress by the Constitution, nor prohibited by it to the states, are reserved to the states respectively, or to the people. What we are about to consider are certainly not delegated to congress, nor are they noticed in the prohibitions to states; they are therefore reserved either to the states or to the people. Their high nature, their necessity to the general security and happiness will be distinctly perceived.
In the second article, it is declared, that a well regulated Militia is necessary to the security of a free state; a proposition from which few will dissent. Although in actual war, the services of regular troops are confessedly more valuable; yet, while peace prevails, and in the commencement of a war before a regular force can be raised, the militia form the palladium of the country. They are ready to repel invasion, to suppress insurrection, and preserve the good order and peace of government. That they should be well regulated, is judiciously added. A disorderly militia is disgraceful to itself, and dangerous not to the enemy, but to its own country. The duty of the state government is, to adopt such regulations as will tend to make good soldiers with the least interruptions of the ordinary and useful occupations of civil life. In this all the Union has a strong and visible interest.
The corollary, from the first position, is, that the right of the people to keep and bear arms shall not be infringed.
The prohibition is general. No clause in the Constitution could by any rule of construction be conceived to give to congress a power to disarm the people. Such a flagitious attempt could only be made under some general pretence by a state legislature. But if in any blind pursuit of inordinate power, either should attempt it, this amendment may be appealed to as a restraint on both.
I would want that his defense did not rely so heavily on the specific wording of A2, such that it could be extended to the remainder of the BOR as well, however it needs to be said that with A2 intact the remainder of our rights lie safely within our ability to defend.