As long as there is clear separation from church and state it wouldn't be illegal I suppose, just as implementing laws based on the zodiac isn't either.
Is that really the world you long for though? Just changing from one dogmatic ruler to the next and obeying their whims.
I always thought we'd continually modify and enhance our world as we learned more and more. That is why I am proud to call myself a progressive, I am a fan of PROGRESS. I don't think we should live today based on how much we knew about the world, ourselves, economy, life, death, war, peace 1000 years ago (or more or less).
We should be able to elect responsible leaders who can put their heads together and make intelligent decisions. We don't see a lot of that anymore, instead we see people pandering to one strong belief or another, and money will guide us the rest of the way.
You can't talk about doing things intelligently and the best possible way without being labeled an idealist either, so there really is no winning. Good thing for myself and others is, just like the fundamentalists, the people who long for a theocracy, the people who would love an authoritative state, we also won't just give up and roll over, we'll continue to blast ignorance with truth, and I do believe truth will ultimately win out in the end, not money, not dogma, not pandering to the lowest common denominator, and certainly not outright lies.