There are so many ailments that can be cured or eased by Cannabis, that I personally find it surprising that it is not on prescription.
I have heard that some Doctors will give you a letter, (to say it's would help with your particular ailment,) for you to give to a 'licenced' provider.
The letter I hear covers the 'provider'.
I did tackle my Doctor about it, he said I would have to be referred to a 'Neurologist', who would only prescribe it if I had 'M.S'. (Multiple Sclerosis'.) So he was pretty sure I could not get it 'legally'. :?
There are just not enough people with conditions that it would help campaigning for it, or it would be available on 'script. :|