Legendary scholar Walter Berns had the following to say about the notion that "Christianity" was part of the "common law." As he wrote in Making Patriots:
Liberty of conscience was widely accepted at the time of the Founding, but this did not prevent some jurists and legislatures from insisting, at least for a while (and given our principles it could be only for a while), that Christianity was part of the law, meaning the common law. So it had been in England, and so, it was assumed by some (but not Jefferson), it would continue to be in America. But there was no disagreement about the place of the common law. Indeed one of the first things done by the states after independence was to declare (here in the words of the New Jersey constitution of 1776) that “the common law of England, as well as so much of the statute law, as have been heretofore practiced in this Colony, shall remain in force, until they shall be altered by a future law of the Legislature; such parts only excepted, as are repugnant to the rights and privileges contained in this Charter [or constitution].”
But if the “rights and privileges” contained in the various state charters or constitutions included the right of liberty of conscience, and if, in turn, this right required, in Madison’s words, “a perfect separation between ecclesiastical and civil matters,” what did it mean to say that Christianity was part of the common law? Very little, as it turned out; and it turned out as it had to turn out. Consider, for example, the case of blasphemy in America…. pp. 32-33.Berns then went on to note that to the extent that blasphemy prosecutions survived for a short period of time in the early American republic, it was redefined as something akin to a secular breach of the peace, with blasphemy now stripped of its religious character.
Berns' recitation of the above quoted part of the 1776 New Jersey constitution also illustrates the proper place the common law of England had in the newly founded America, in terms of its priority as a source of law: And that is, common law is below state statutory law. Later court decisions -- notably Erie v. Tompkins -- would hold that there is no such thing as general federal common law, consigning such common law to the state level entirely.
Still, we debate whether some kind of "organic" law exists in the brooding omnipresence in the sky up there, that could potentially inform all sources of law (from higher to lower). That such organic law, if needed, could serve potentially as the ultimate trump existing above the highest source of constitutional positive law.
That's where such a theory becomes controversial. If the uncodified, "brooding omnipresence" is consigned to a place where a state statute can trump it, such seems more contained, hence less controversial. If, on the other hand, it's justiciable by the Supreme Court (and American courts in general) and exists at a place higher than the US Constitution, such a powerful thing in the hands of judges becomes understandably more controversial.
What prevails among the experts in academia, government and the practice of law is legal positivism. Such teaches that "higher law," if it exists at all, is nothing judges may consult in their legal decision making outside of the existing positive law.
I think of someone like the late Justice Scalia, who was a devout Roman Catholic, believing in the natural law as his church taught it. But, he argued, such had no business informing judicial decision making. Rather, it was something legislators could consult in the realm of conscience (the executive could consult such as well when deciding for instance, whether to veto a law).
Just as the other non-judicial branches could, as they exercised their political power, consult whatever kind of specific revelation they wanted: Catholic, Protestant, Mormon, Jewish, Hindu, Islamic, etc. Or whatever kind of ethical or political theory they fancied: Utilitarianism, Kantianism, Rawlsianism, etc.
After meticulously studying, for many years, the concept of this organic law of the brooding omnipresence as it was understood by America's founders, I have concluded the Christian religion, special revelation, etc. is not the source of such, even though such did often claim to have theistic underpinnings (i.e., the "Laws of Nature and of Nature's God").
Yet, we still have this notion coming from Blackstone himself that "Christianity is part of the common law." As noted above by Professor Berns, Jefferson disputed such a notion. But what might we make of such a notion, if applicable to the newly minted America of the late 18th and early 19th Century?
American founder and preeminent legal authority St. George Tucker (of Virginia) provided the answer as to what he understood the theology of the common law to be. I just completed a series where I reproduced Tucker's lengthy discussion on religion and politics, contained in Philip B. Kurland's "The Founders' Constitution" under the title of "St. George Tucker, Blackstone's Commentaries." In 1:App. 296--97, 2:App. 3--11 of said document, Tucker discusses, at length, his opinions relating to religion and government.
In this 1803 document, Tucker invokes the then existing state laws of Virginia and the US Constitution. He also includes a tremendous amount of words from (the Arian) Richard Price's "Observations on the Importance of the American Revolution and the Means of Making It a Benefit to the World" where Price explicates his Enlightenment ideal of religion and politics. This ideal is not wholly secular, but rather seems informed by an Enlightenment faith more "fit" for that era.
Here is a quotation from such (Tucker quoting Price) that encapsulates such zeitgeist:
It is indeed only a rational and liberal religion; a religion founded on just notions of the Deity, as a Being who regards equally every sincere worshipper, and by whom all are alike favoured as far as they act up to the light they enjoy: a religion which consists in the imitation of the moral perfections of an Almighty but Benevolent Governor of Nature, who directs for the best, all events, in confidence in the care of his providence, in resignation to his will, and in the faithful discharge of every duty of piety and morality from a regard to his authority, and the apprehension of a future righteous retribution. ... This is the religion that every enlightened friend to mankind will be zealous to support. But it is a religion that the powers of the world know little of, and which will always be best promoted by being left free and open.One might ask, why did Tucker reproduce Price's thoughts on religion and politics in a document meant to capture Blackstone's authoritative teachings on the common law? The answer relates to purpose of Tucker's Blackstone project. Tucker meant more than just to reiterate Blackstone's teachings, but to transform and correct them for America.
The following article by law professor Kurt Lash uncovers such purpose:
[T]he same generation that adopted the Constitution also challenged the uncritical acceptance of English common law. ...
For example, St. George Tucker’s 1803 edition of Blackstone’s Commentaries was a hugely successful and influential effort to “translate” the rules of English common law so that they made better sense for a people whose legal system presumed the ultimate sovereignty of the people themselves.31 The United States was not just a new and independent legal entity, the country and its citizens had operationalized a new legal theory. The status of the government and the role of its courts were different on American soil, rendering problematic any wholesale adoption of Blackstonian common law. As historian Davison Douglas writes:
"While serving as a law professor at The College of William and Mary during the 1790s, Tucker had his students read Blackstone, but he supplemented that reading with lectures in which he analyzed the ways that law in the United States—and specifically Virginia—had departed from English legal principles as a result of the American Revolution, the Virginia Constitution, and the United States Constitution. These lectures were “the first systematic effort by any figure in American law to describe the contours of the new system created by the amended Constitution.” Drawing extensively on his William and Mary lectures, Tucker’s Blackstone included eight hundred pages of essays on a variety of legal and political topics and more than one thousand footnotes in which Tucker examined Blackstone in light of American and Virginian law. Tucker worried about the effect Blackstone’s Tory sensibilities might have on his students. He thus emphasized to his students that the American Revolution and its aftermath had produced a revolution “not only in the principles of our government,” but in a variety of legal principles, such as the law of inheritance, that reflected the new nation’s republican values and that rendered Blackstone an unreliable guide to certain aspects of American law."
St. George Tucker’s “translation” of Blackstone found an eager audience. Again, according to Douglas,
"Tucker’s Blackstone, the first major legal treatise on American law, was one of the most influential legal works of the early nineteenth century and the most comprehensive treatise on American constitutional law until around 1820. Not surprisingly, it was also one of the legal texts most frequently cited by the United States Supreme Court and relied upon by lawyers appearing before the Court during the first few decades of the nineteenth century."33So I'm guessing that all of the material on religion and government complete with Richard Price's ideal kind of theology was Tucker's answer to Blackstone's claim that "Christianity is part of the common law."