The Law and Neuroscience

i cannot understand why people say that if it is shown that peoples actions are completely determined by their chemical makeup that it is some sort of legal delemma as to weather or not they can be held responsible for their crimes. We are talking about two differnt levels of reality here. If we decide to look at everything in terms of chemicals, we can no longer talk about “people” or “legality” or any other abstract construct that does not exist at that level. People can do legal/illegal things. Chemicals cant. So if we are gonna say that chemicals describing peoples actions illeviates them from responsibility, then we may as well scrap all legal, political and moral structures that exist today.