Came across this post today and it gave me something to think about though. Enjoy!
Citizens of any given country are bound by the laws of that country and each country has got a system of taxation in place which all its citizens have to abide by. When Israel left Egypt, they left as a nation. And God proceeded to give them the constitution for this new nation in the form of the law. Since there was no separation between church and state, religion played a very important part in their everyday life and it governed how they lived.
Their constitution forbade them from intermarrying with certain tribes, prohibited them from working on the Sabbath day and also governed the way slaves and fellow citizens were treated. Since Israel was a theocracy, God was their king and it is the right of every ruler to establish the constitution of the country he governs.