For those people who LEGALLY grow or consume medicinal marijuana (and ONLY you)
Pot needs to be metabolized prior to consumption. THC must be converted to D9-THC. To do this, it simply must be heated. that is why you can smoke it. If you take raw plant matter and eat it, nothing will happen. To eat pot for its MEDICINAL effect, it must be cooked. The best way to do this is to saute in butter... heat metabolizes the THC and the fat from the butter extracts it from the plant matter. that butter can then be used as you normally would in the kitchen.
So, I imagine one could use the buds of a female pot plant as a late addition (10 min or less, maybe) and have D9-THC, but then to extract that from the plant matter and incorporate that into the wort would require a fat... something that we brewers try to avoid (head retention).
Alcohol may also be capable of extracting THC from the plant matter, but you still need to heat it first...
Any ideas?