That, I would suggest is part of Founding natural law-natural rights theory as put forth by Jefferson and Madison and encapsulated in the Declaration of Independence: We have a natural right -- under our unalienable rights to liberty, pursuit of happiness and the property that each man has in himself -- to do what is arguably immoral conduct.
Ed Feser addresses some of these issues in his new article on TCS. The thesis of the article is that Hayek was more of a traditional conservative than libertarians would desire (but that his ideas will also leave traditional conservatives wanting). I don't know enough about Hayek to respond. I'm more interested in what Feser has to say on Locke and Aquinas and how that might relate to the natural law/natural rights theory which founds America's public order.
First Feser on Aquinas' classical natural law theory:
On the classical sort of natural law theory deriving from thinkers like Thomas Aquinas - the kind often appealed to in support of traditional morality - rights are grounded in moral duties. What I have a right to do is just whatever I am obliged to do under natural law, or to what is a necessary prerequisite of performing my obligations. That is the reason rights exist at all - they are safeguards of our ability to fulfill the natural law and flourish as the kinds of beings we are. Hence there can be no such thing as a right to do wrong; the very idea is incoherent. Yet that is exactly what libertarians claim we have - they say, for example, that a person has, all things being equal, a moral right to inject heroin into his veins even if it would be immoral for him to exercise this right. From a classical natural law point of view, this is just muddleheaded. There may well be reasons for government to tolerate certain immoral activities - classical natural law thinkers do not necessarily endorse paternalism, and in fact are often wary of it - but rights per se can have nothing to do with the matter.
Now, this may be true. But as I will show, Founding natural law/natural rights theory does indeed hold that individuals, in principle, have a natural right to do wrong. Therefore, if this contradicts the classical natural law understanding of "rights" (I put that in quotes because Allan Bloom et al. would point out that there are no "rights" under the classical theory of nature, only duties), this simply informs that the theory of natural rights in the Declaration broke with the traditional classical understanding of nature via Aquinas.
Feser moves on to Locke:
Why then do some libertarians claim that natural law supports their view? Some no doubt assume that since John Locke was both a natural law theorist and an influence on libertarians like Robert Nozick, natural law must support libertarianism. But Locke himself was not a "libertarian" as that term is generally understood, and his version of natural law, while very different from the sort that traces its lineage back to Aquinas, hardly leads in a libertarian direction. For Locke, our rights are grounded in God's ownership of us. Strictly speaking, to say that each human being has a right to his life, liberty, and property is just shorthand for saying that we have a duty not to kill, enslave, or steal from others because to do so would be to damage what belongs to God. But by the same token, we have no right to do what is harmful to ourselves either, for this too would damage God's property - hence Locke's explicit denial that we have any right to commit suicide. No libertarian could plausibly make a Lockean case, then, for drug legalization, physician-assisted suicide, or any other such practice on the grounds that it only harms the one doing it.
Now, here is where Feser doesn't give us the entire story. And he is, I would argue, wrong to suggest that no plausible Lockean case can be made for libertarianism. Richard Epstein and Randy Barnett come to mind as folks who do exactly this. Feser takes a jab at Barnett when he next writes:
Other libertarians would appeal to a conception of "natural law" that makes no reference either to God (as Locke does) or to an unchanging metaphysical human essence (as followers of Aquinas do). Instead, it holds only that there are certain empirical facts about the human condition that we ought to keep in mind in our moral and political decision making, "natural laws" about human biology, psychology, and social organization analogous to the laws of nature uncovered by physical science. But this rather banal claim really has nothing particularly to do with natural law theory as it has historically been understood; it is certainly not what Aquinas and other medieval thinkers meant by "natural law."
But Randy Barnett precisely appeals to a branch of Lockean thought in making his claim. Indeed, a very important branch -- the Jeffersonian-Madisonian understanding of Locke that is contained within our natural rights Founding documents.
One thing I've learned in studying various prominent thinkers is that their ideas aren't contained in a vacuum and invariably evolve when put into the hands of their followers. Often their ideas "branch off" in different directions, with opposing schools of thought ultimately tracing their lineage back to the same thinker. Endless examples could be offered for this. To give one, in debating whether Calvinism is consistent with the concept of revolt, I've learned that while Calvin himself seemed to be quite clear that revolt is never permitted, some later followers of his -- "Calvinists" -- were more generous in recognizing a right to revolt against tyranny. Others believed, after Calvin himself, that the Bible, in no uncertain terms, forbade revolt against civil government.
On religious liberty itself, Locke wouldn't extend it to, among others, atheists and Catholics. In Jefferson's notes on Locke, he wrote: "Locke denies toleration to those who entertain op[inio]ns contrary to those moral rules necessary for the preservation of society." Then Jefferson noted, "But where he stopped short, we may go on." Jefferson's and Madison's "Lockeanism" lead them to hold that the unalienable rights of conscience apply equally to all, to "the Jew and the Gentile, the Christian and Mahometan, the Hindoo, and Infidel of every denomination."
In his book "Notes on the State of Virginia," Jefferson put it as follows:
"[O]ur rulers can have no authority over such natural rights, only as we have submitted to them. The rights of conscience we never submitted, we could not submit. We are answerable for them to our God. The legitimate powers of government extend to such acts only as are injurious to others. But it does me no injury for my neighbor to say there are twenty gods or no god. It neither picks my pocket nor breaks my leg."
Now, by holding that men have the natural right to openly worship false gods or profess atheism, Jefferson necessarily held that men have a natural right to do what may be wrong, because the Bible holds these things to be wrong. In fact, they violate the very First Commandment of the Bible, and elsewhere in the Old Testament, public proselytizing for false gods, like sodomy, merits execution. Indeed, for a thousand and some hundred years, before Church and State were separated in the West, in various "Christian Nations" one could be executed for heresy, blasphemy, worshipping false gods, or for generally violating one's duties to God. Now, thanks to Jefferson and Madison, most of these things are protected under the First Amendment's right to Free Exercise of Religion.
To put this into perspective, many of America's Colonies founded under an earlier order, had laws on the books which demanded execution for violating the "First Tablet" of the Ten Commandments. For instance, the Massachusetts Body of Liberties held:
(Deut. 13. 6, 10. Deut. 17. 2, 6. Ex. 22.20)
If any man after legall conviction shall have or worship any other god, but the lord god, he shall be put to death.
Nearly all of the colonies save Rhode Island, when founded, had similar laws. Jefferson and Madison flipped this notion on its head by arguing that men have an unalienable God given right to worship no god or twenty Gods. It shouldn't surprise then that some argue Jefferson's and Madison's rights-granting "Nature's God," because He seems not jealous, is not the Biblical God. Likewise, though many orthodox Christians, mainly dissenters, supported Madison's and Jefferson's project and found ways to reconcile Lockean-Jeffersonian-Madisonian theory with their understanding of the Bible and the Christian religion, other pious Christians, those more sympathetic to the older order, could not.
In reflecting on the above quoted passage from Notes on the State of Virginia, the Reverend John Mason termed Jefferson's idea
the morality of devils, which would break in an instant every link in the chain of human friendship, and transform the globe into one scene of desolation and horror, where fiend would prowl with fiend for plunder and blood -- yet atheism "neither picks my pocket nor breaks my leg." I will not abuse you by asking, whether the author of such an opinion can be a Christian?
Clearly then, if one believes that breaking the first tablet of the Decalogue is immoral, then Jefferson and Madison, building upon a Lockean foundation, believed men had a natural right to do wrong.
I also disagree that Locke's notion of self-ownership does not support libertarianism. In fact, when libertarians argue that they have a right to use illegal drugs or commit suicide they do so precisely because of the Lockean notion that an individual belongs to himself. Feser writes that Locke believed "we have no right to do what is harmful to ourselves either, for this too would damage God's property." For one, this ignores the tension, long discussed by serious scholars of Locke -- the Straussians -- between the notion that an individual belongs to himself and that an individual belongs to God. See my past post where I discuss an article that Harvey Mansfield wrote on the matter. As he put it:
Locke gives two descriptions of the character of men in their fundamental relation to liberty. He says that they are the "workmanship" of God, that men are "his [God's] property" and so belong to God; but he also says that "every man has a property in his own person."1 These appear to be directly contrary because the "workmanship argument" (as it is called by Locke's interpreters) would make man a slave of God2 whereas the idea of property in one's own person sets him free to do with himself what he wishes. Thus Locke says, in accordance with the former, that men have no right to commit suicide ("everyone is bound . . . not to quit his Station wilfully"3). But in accordance with the latter, though saying nothing directly about a right of suicide, he pronounces that in the state of nature, man is "absolute lord of his own person and possessions."4
...The difference between belonging to God and belonging to yourself is not a small one....
Indeed, in Bowers v. Hardwick, Justice Blackmun's dissent uses the self-ownership premise to argue for a "right" to commit "sodomy" because he believed, as did Locke, "that a person belongs to himself and not others nor to society as a whole."
It's possible that, in committing "sodomy," men are ultimately doing something wrong because God or nature forbids such activity (personally I don't believe it). Even so, it does not follow that men have no natural right to "sodomy." An analogy, again, can be raised to the rights of conscience. Jefferson was well aware that many thought it gravely immoral to profess atheism, deny the Trinity, worship idols or otherwise violate the first table of the Decalogue. His response: "We are answerable for [how we exercise our rights of conscience] to our God" and not our fellow man in the civil compact. Locke likewise held that "The care, therefore, of every man's soul belongs unto himself," not government.
I don't see how -- according to Lockean thought -- the care for a man's body necessarily must differ from the care for man's soul. Both are, according to Locke, God granted unalienable rights for which we are ultimately responsible to God and not fellow man or government. Therefore, if one harms himself physically as he might harm his soul by breaking the first tablet of the Decalogue, man is still responsible to God only and not fellow man or government.
And again, this is how Jefferson seemed to have interpreted Locke. In the above quoted passage from Notes on the rights of conscience Jefferson seemed to blur the soul/body line in terms of what government, by right, may do:
The legitimate powers of government extend to such acts only as are injurious to others. But it does me no injury for my neighbor to say there are twenty gods or no god. It neither picks my pocket nor breaks my leg.
Similarly, if Jefferson's neighbor does drugs or commits suicide it still neither picks his pocket nor breaks his leg. And while I am not aware of Jefferson ever speaking on drugs (though he was an avowed pleasure-seeking Epicurean), he did apparently oppose criminal sanctions for suicide:
Men are too much attached to this life to exhibit frequent instances of depriving themselves of it. At any rate, the quasi-punishment of confiscation will not prevent it. For if one can be found who can calmly determine to renounce life, who is so weary of his existence here as rather to make experiment of what is beyond the grave, can we suppose him, in such a state of mind, susceptible to influence from the losses to his family by confiscation? That men in general disapprove of this severity is apparent from the constant practice of juries finding the suicide in a state of insanity; because they have no other way of saving the forfeiture.
And while Locke didn't believe man had a right to committ suicide, he did, right after he asserted "[t]he care...of every man's soul belongs unto himself," compare the care for man's soul to care for his physical property and body and made a very libertarian sounding argument:
But what if he neglect the care of his soul? I answer: What if he neglect the care of his health or of his estate, which things are nearlier related to the government of the magistrate than the other? Will the magistrate provide by an express law that such a one shall not become poor or sick? Laws provide, as much as is possible, that the goods and health of subjects be not injured by the fraud and violence of others; they do not guard them from the negligence or ill-husbandry of the possessors themselves. No man can be forced to be rich or healthful whether he will or no.
So it appears that short of suicide, Locke believed that man did indeed have a right to do injury to himself or his estate. And the notion that "[l]aws provide...that the goods and health of subjects be not injured by the fraud and violence of others; they do not guard them from the negligence or ill-husbandry of the possessors themselves" is remarkably close to what today's libertarians argue.
Finally, if I may speculate on Feser's motives in attempting to overstate the difference between Locke's writings and modern libertarianism, it is because Feser, as a political opponent of libertarianism, wants to weaken its theoretical underpinnings. But Locke's words speak for themselves and his principle of self ownership persists as viable, useful, and foundational to American Founding thought, in spite of attacks that fall short.