My point is simply that claims of the explanatory power of theories are often not all what they are advertised to be.
What are/is the brute law(s) that allow the mental and physical to create consciousness?
What do you mean brute law? Are you asking what laws of physics the phenomenon of consciousness can be reduced to? One feature of an emergent phenomenon is that it transcends lower order laws. In a sense, it operates in a way that no lower order law could predict(at least with our feeble intellects).
So in a sense, consciousness has its own set of laws, layered on top of the laws that govern the operation of nervous systems, which are layered on top of the laws that govern basic biological systems, which are layered on top of the laws of physics. All of these layers supervene on the ones below, but to digest them wholesale is beyond our ability. Which I why we break things down into bite sized layers.
So my simple answer is I have no freaking clue. To say something is an "emergent phenomenon" is one part ignorance, one part explanation. The explanation is that the phenomenon supervenes on other systems. This isn't much as far as explanations go, but it is the best we can currently do and still be have an intellectually humble answer. It does allow us to say a few things, and offers a framework for further explanation. So it is more than mere ignorance.