Sooooooo why exactly would you take the 10 commandments into law making anyway exactly?
There are 3 reasons that judges would use foreign law to make decisions, two of which apply to the commandments.
#1, to decide the status of analogous status in the US. For example, if you need to decide the adoption status of a child in the US with a biological parent in Mexico, it may be relevant what the law of Mexico says about that parent's legal responsibilities. Not relevant to the 10 commandments, though.
#2, sentencing. US judges are free to use almost any source in making their sentencing decisions, except those that are explicitly discriminatory. I don't believe this is a violation of the establishment clause, but don't quote me on it. So a US judge could use the standards of the commandments to decide how bad a specific instance of a crime was. It would not be permissible to use the commandments to discriminate on the basis of sex or race, though, because that would violate the equal protection clause, and discriminating on the basis of religious status would, I imagine, violate the establishment clause. But it's certainly possible to consider the substance of the commandments without considering the status of the offender, of course.
#3, arbitration. A number of contracts have arbitration clauses that say that if there's a dispute about the terms of the contract that it be decided by an arbitrator instead of the court system. this allows parties to save the money and trouble that a full trial would demand. The decisions of arbitrators are subject to review by the courts, but the rules by which they make decisions are not. In other words, if an arbitration clause calls for a decision by an imam according to Sharia law, the only thing that courts can review is whether the imam ruled correctly (technically, reviewing the decision for "abuse of discretion" by the arbitrator) according to sharia, even if the code itself discriminates on the basis of sex or anything else (which it does, btw.) Same thing appplies if it calls for decision based on Canadian law, or any other countries'. Unclear what the OK law would mean for arbitration, but it's clear that a judge can't review an arbitration decision without understanding what the code the decision was made under means.
