Hm, I didn't realise that, djonkoman, thanks for the correction.actually, there's plenty of this stuff with legal crops too.
but they have upov(https://en.wikipedia.org/wiki/International_Union_for_the_Protection_of_New_Varieties_of_Plants) , and whenever there's a dispute they can just go to court and let the judge settle it.
No doubt such disputes will arise wherever there's moolah involved, though.
So perhaps in some future cannabis market, if someone developed a strain that really worked, say, for arthritis (random example), then I could see they might want a patent of some sort, if their purpose was to make money.
Wouldn't affect 99%+ of us though (well, not unless nothing else worked for arthritis).
Who would really go to an expensive medical dispensary if weed were totally free?