I think legally, CS is much different than non-CS. For non-cs drugs, I think that the legislation is purposely vague because it is always a judgment call on the part of the MD/pharmacist on whether or not it is ok to prescribe/fill self-written drugs based on the individual case. Some things (emergencies, maintenance Rxs in a pinch, etc..) are usually clearly ok, some things are clearly not, and some things aren't so clear at all. For controlled substances, at least in the state I practice in, it is always illegal to prescribe for yourself or immediate family and for all cs Rxs there must be a "bona fide physician-patient relationship" and documentation of the prescription in a medical record