A commenter in a thread below questioned the plausibility of the view that "security of a free State" in the Second Amendment could mean "security of a free country," as opposed to security of one of the States of the Union against federal oppression.

Well, it turns out that talk of what institutions -- especially military ones -- are good for a free state is all over Blackstone's influential Commentaries on the Law of England. There, of course, Blackstone had to have been talking of state in the sense of country or nation (American states as subordinates in a federal system were a decade in the future). Consider, for instance, book 1, p. 408 (emphasis added):

In a land of liberty it is extremely dangerous to make a distinct order of the profession of arms. In absolute monarchies this is necessary for the safety of the prince, and arises from the main principle of their constitutions, which is that of governing by fear: but in free states the profession of a soldier, taken singly and merely as a profession, is justly an object of jealousy. In these no man should take up arms, but with a view to defend his country and it's laws: he puts not off the citizen when he enters the camp; but it is because he is a citizen, and would wish to continue so, that he makes himself for a while a soldier.

Or book 1, p. 415 (emphasis added):

To prevent the executive power from being able to oppress, says Baron Montesquieu, it is requisite that the armies with which it is intrusted should consist of the people, and have the same spirit with the people; as was the case at Rome till Marius new-modeled the legions by enlisting the rabble of Italy, and laid the foundation of all the military tyranny that ensued. Nothing, then, according to these principles, ought to be more guarded against in a free state than making the military power, when such a one is necessary to be kept on foot, a body too distinct from the people.

Or book 1 p. 417 (emphasis added):

Nor is this state of servitude [created by excessively rigorous military discipline during peacetime] quite consistent with the maxims of sound policy observed by other free nations. . For, the greater the general liberty is which any state enjoys, the more cautious has it usually been of introducing slavery in any particular order or profession. These men, as baron Montesquieu observes, seeing the liberty which others possess, and which they themselves are excluded from, are apt (like eunuchs in the eastern seraglios) to live in a state of perpetual envy and hatred towards the rest of the community; and indulge a malignant pleasure in contributing to destroy those privileges, to which they can never be admitted. Hence have many free states, by departing from this rule, been endangered by the revolt of their slaves: while, in absolute and despotic governments where there no real liberty exists, and consequently no invidious comparisons can be formed, such incidents are extremely rare. Two precautions are therefore advised to be observed in all prudent and free governments; 1. To prevent the introduction of slavery at all: or, 2. If it be already introduced, not to intrust those slaves with arms; who will then find themselves an overmatch for the freemen. Much less ought the soldiery to be an exception to the people in general, and the only state of servitude in the nation.

Likewise, Blackstone refers to what is good for free states in discussing the liberty of the press ("The liberty of the press is, indeed, essential to the nature of a free state," book 4, p. 151), in discussing the value of popular government ("In a free state every man, who is supposed a free agent, ought to be in some measure his own governor," book 4, p. 158) -- and in praising what he saw as the calming force of the established Church of England (book 4, p. 104):

[R]eligious principles, which (when genuine and pure) have an evident tendency to make their professors better citizens as well as better men, have (when perverted and erroneous) been usually subversive of civil government, and been made both the cloak and the instrument of every pernicious design that can be harboured in the heart of man. The unbounded authority that was exercised by the druids in the west, under the influence of pagan superstition, and the terrible ravages committed by the Saracens in the east, to propagate the religion of Mahomet, both witness to the truth of that antient universal observation: that in all ages and in all countries, civil and ecclesiastical tyranny are mutually productive of each other. It is therefore the glory of the church of England, that she inculcates due obedience to lawful authority, and hath been (as her prelates on a trying occasion once expressed itc) in her principles and practice ever most unquestionably loyal. The clergy of her persuasion, holy in their doctrines and unblemished in their lives and conversation, are also moderate in their ambition, and entertain just notions of the ties of society and the rights of civil government. As in matters of faith and morality they acknowlege no guide but the scriptures, so, in matters of external polity and of private right, they derive all their title from the civil magistrate; they look up to the king as their head, to the parliament as their law-giver, and pride themselves in nothing more justly, than in being true members of the church, emphatically by law established. Whereas the notions of ecclesiastical liberty, in those who differ from them, as well in one extreme as the other, (for I here only speak of extremes) are equally and totally destructive of those ties and obligations by which all society is kept together; equally encroaching on those rights, which reason and the original contract of every free state in the universe have vested in the sovereign power; and equally aiming at a distinct independent supremacy of their own, where spiritual men and spiritual causes are concerned.

And life in a free state may also be reason to suffer some inconvenience, book 3, p. 423 (paraphrasing Montesquieu):

But in free states [unlike despotisms such as Turkey] the trouble, expense, and delays of judicial proceedings are the price that every subject pays for his liberty ....

Montesquieu generally used "a free state" in similar ways: "In a free state, every man, who is supposed a free agent, ought to be concerned in his own government: Therefore the legislative should reside in the whole body of the people, or their representatives"; see also the references to "a free state" in this, albeit later, translation of Montesquieu's The Spirit of Laws.

"State" as "country" (or perhaps more precisely a self-governing nation) is of course pretty longstanding usage; article I, section 9, for instance, bars federal officeholders from accepting presents or titles from "any ... foreign state." Article III, section 2 and the Eleventh Amendment likewise use "foreign state" to mean foreign country. But beyond this, "a free state" as indicating what Englishmen and Americans should cherish and aspire to, is right from Blackstone and other contemporaneous writers.