When we talk about the legal systems of the world, there comes to mind Cannon Law (Roman Catholic), Hindu Law, Jewish Law, and Islamic Law (Shariah), to name a few.
In Afghanistan, for example, in the hierarchy of laws, Shariah rules supreme, above the country’s Constitution. I have never been an “expert” on Islamic Law, but I have found plenty of written resources that have helped me understand the natural tension between the religious law and the secular law.
Here is an interesting compilation of “religious laws in a nutshell” from NYU’s Hauser Global Law School Program. And here is the Practitioners’ Guide on Islamic Law written by Mr. Hamid Khan for the International Network to Promote the Rule of Law (INPROL), which I highly recommend to anyone who is interested in the Rule of Law.