A forthcoming edition of the International Journal of Constitutional Law includes an article by Harvard professors Adam Shinar and Anna Su entitled, "Religious Law as Foreign Law in Constitutional Interpretation." The abstract is below
This article challenges the conventional understanding of the separation of church and state by arguing that there is no analytical or constitutional problem with using religious law for the purpose of constitutional interpretation. We situate our arguments within the context of the broader debate on the use of foreign law in constitutional interpretation, and the more recent controversy surrounding the proposed bans on the use of religious law in U.S. state courts. By examining the arguments for and against the use of foreign law, we show how they equally apply to the use of religious law. More importantly, we conclude that differences between foreign law and religious law are, at best, differences of degree rather than kind, and thus do not militate against the use of religious law in constitutional interpretation. The article demonstrates that religious law can be used, and in fact, has already been used by the Supreme Court for four limited purposes, none of which, we argue, offends the principles underlying the Establishment Clause.
The ultimate import of our claim is not that religious law should be used by courts, but that recognizing its potential as a source in constitutional interpretation should result in a deeper and more careful engagement with the possibilities it generates.
The U.S. Constitution is a common law document and the common law is founded upon ancient custom, natural law and right reason. As such, natural law would seem to be a logical and legitimate source by which to interpret the U.S. Constitution - and religious law would seem to be a promising guide by which to discover the natural law. However, entrusting judges with the authority to scrutinize religious law and decipher the natural law seems to be nothing more than conservative rhetoric for the adoption of a "living constitution."
Furthermore, the authors - who seem to favor the adoption of foreign law in U.S. courts - are not likely contemplating Catholic canon law or Jewish Halakha, but rather Islamic Sharia law. Those who might feel inclined to sympathy toward the use of religious law in U.S. courts should consider well which religious law will be employed and the likelihood that religious law would be subverted to bolster progressive ends which will prove anathema to those of faith.
Insofar as religious law - and religion itself - historically cultivated American law, it is a relevant and proper guide to the interpretation of the original meaning of the constitution's text. But as a persuasive authority to which judges may turn for inspiration in updating an evolving constitution, religious law is no less dangerous than French law.
H/t: Mirror of Justice.