California is still under the IBC, as are a couple of other areas of the US, but neither the IBC nor UBC preclude rammed block or rammed earth building. Really, you just have to convince your local building department it meets all the requirements of code. Rammed earth will actually help you out quite a bit with energy code and get you a few points for LEED. Rick Joy, who works out of Tucson, does some beautiful work. Google image search him if you're interested.