I don't know about tenant laws beyond how to get my deposit back, lol, but as far as no prescription only recommendation - what I wrote above about the CA state patient card, that exactly what it is - the state checks and recognizes your doctor's recommendation and makes you 'official' on state level. You get a patient card from the state of CA. At that point you are protected directly under the state laws. That should have some weight. Don't think there have been any CA Superior Court cases on this particular issue but sooner or later there will be.
And that would be a sad day for the Constitution. A tenants right to screw up my house and possibly get it federally seized would not trump my right to my property.
I can deny a tenant just for looking funny, that's the owners right just as it is a store's right to refuse service to anyone for any reason.
Even if the state make you more official sounding with a state card as opposed to a county ID, at the end of the day I have final say as to who does what on my property. For example you don't have the right to overload my breaker box or rewire my setup to suit your medical needs. I don't have to widen my doors or re-equip my bathroom if you are in a wheelchair....same difference but the nail in the coffin is that its not a federal crime to be in a wheelchair.
I believe everyone has the right to grow I truly do....everyone has the right to do anything that doesn't infringe on anothers rights....you have the right to purchase your own home and do what ever in it I would never advocate against that....once you have purchased your own home you have the right to rent it out, under your own stipulations just as the video store puts parameters on what you can and cant do with their movie.
At the end of the day you need to either have your landlord's permission or keep it on the DL.
The Federal card can be played at any time.