When I first started blogging on the issue of the political-theology of the American founding many years ago, I grappled with the notion that blasphemy laws continued to exist in the United States under its constitutional order. I quoted the following from the late Straussian scholar Walter Berns in his book "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.
This site from the Library of Congress notes something similar:
One of the first recorded instances of someone being convicted for blasphemy in the state of New York occurred in 1811. In People v. Ruggles, the New York Supreme Court upheld the conviction, saying that the crime of blasphemy is “independent of any religious establishment,” and that it affects “the essential interests of civil society.” In 1824, the Pennsylvania Supreme Court similarly upheld a conviction for blasphemy in Updegraph v. Commonwealth. That court also concluded that blasphemy laws seek “not to force conscience by punishment, but to preserve the peace of the country….” Two more similar cases came down in the 1830s, with State v. Chandler in 1837 and Commonwealth v. Kneeland in 1838. In these cases, the Delaware Supreme Court and the Massachusetts Supreme Court both upheld blasphemy convictions on the grounds that they were meant to preserve public peace rather than punish beliefs.
Because these cases involved state law, the outcomes and rationales for them could differ. The Chandler decision gives a secular, pluralistic rationale for blasphemy laws:
If in Delaware the people should adopt the Jewish or Mahometan religion, as they have an unquestionable right to do if they prefer it, this court is bound to notice it as their religion, and to respect it accordingly.
...
It will be seen then that in our judgment by the constitution and laws of Delaware, the christian religion is a part of those laws, so far that blasphemy against it is punishable, while the people prefer it as their religion, and no longer. The moment they change it and adopt any other, as they may do, the new religion becomes in the same sense, a part of the law, for their courts are bound to yield it faith and credit, and respect it as their religion. Thus, while we punish the offence against society alone, we leave christianity to fight her own battles, ...
This is not "Christian Nationalism." Personally, I think blasphemy laws are NOT consistent with notions of "liberty of conscience" or the First Amendment. Here is an interesting letter from John Adams to Thomas Jefferson, dated January 23rd, 1825 wherein he makes that point:
... There exists I believe throughout the whole Christian world a law which makes it blasphemy to deny or to doubt the divine inspiration of all the books of the old and new Testaments from Genesis to Revelations. ... [E]ven in our Massachusett which I believe upon the whole is as temperate and moderate in religious zeal as most of the States A law was made in the latter end of the last-century repealing the cruel punishments of the former laws but substituting fine and imprisonment upon all those blasphemers upon any book of the old Testament or new Now what free inquiry when a writer must surely encounter the risk of fine or imprisonment for adducing any argument for investigation into the divine authority of those books? ... I think such laws a great embarassment. great obstruction to the improvement of the human mind. Books that cannot bear examination certainly ought not to be established as divine inspiration by penal laws. It is true few persons appear desirous to put such laws in execution and it is also true that some few persons are hardy enough to venture to depart from them; but as long as they continue in force as laws the human mind must make an awkward and clumsy progress in its investigations. I wish they were repealed. ...