Both "biblical law" and "Christian law" describe what you're asking for here. I suspect they don't quite have the flavor you're looking for, given the context you describe, but I think they are what you need.
Any other word is likely to be more obscure, and make it look like you're intentionally attempting to start from a position that you consider such law archaic, which will lose you allies.
If you require more specificity, then I suggest you use common terms there too. "Fundamentalist Christian law", for instance, to describe laws that would derive from the Christian corpus, but not necessarily be inline with modern Christian mainline teaching.
You may also need to describe a proposal for such a law as a step back from current law, in which case the adjective "regressive" might be appropriate. A "regressive biblical law" would be a law based on sound bible text, but one which would return society to an ostensibly worse state.
What might be really interesting to pursue is a redundant adjective to use when disambiguating "real" law from these other laws. I've heard "secular law" and "humanist law" in the past year, but both also sound combative in contrast. "Logical law" or "ethical law" both also sound patronizing in contrast. I'm afraid I have nothing better to offer here.