We are all used to the federal government offering only limited deference to states when it comes to medical marijuana. And we are certainly used to it refusing to admit that patients have a legal right to use marijuana for medical purposes, or even that marijuana has medical value at all. Apparently, it also thinks that those who are abiding by state law and using medical marijuana do not have certain constitutional rights, either. In a memo issued last week by the Bureau of Alcohol, Tobacco, Firearms,…