The definition of a valid prescription for a controlled substance
includes the prescription written in the usual course of professional
practice.  What arguments can be made to prove that a prescription can
be legitimate via an online consultation with a physician, using any
court cases to support your argument?  In other words, what support is
there to claim that a prescription written without the old standard
face-to-face examination is a valid prescription?

Face to face doctors often invest as little as 5 minutes, choosing a
perscription drug for a patient, without considering anyone else's
opinion. An on line Doctor with a good staff of researhers should make
no more errors on the average, if they are extra dilligent.
 Should a large claim occur,IMO the lawyers will eat you alive. and
you could get busted by a regulatory agency and/or something like 60
minutes on TV.   Neil