And the only reason they found the stuff while searching the property is because they had a warrant to search the premises for stolen property along with the fact that the son had already been nailed for sale/trafficking previously and gotten a reworked probation.
Also the amount "needed" for pain management is a complete red herring. That many licensed medical professionals are 100% okay with doping people up with ludicrous dosages to simply "manage pain" is an entirely separate topic concerning ethics, drug dependencies, sensory deprivation, etc... but pulling the "you don't know what he needs" as justification is just nonsense. At best it is anecdotal layperson testimony which is entirely countered by the fact that other sufferers of chronic pain (ie myself, from the military no less) can manage their pain WITHOUT pain killers, marijuana, etc.
Also even if we play the hypothetical that marijuana shouldn't be warred against as an illegal drug, it is still a food/drug substance that has monetary value for sale. That means regulation, fines, and even jail sentencing are STILL appropriate in "arbitrary" conditions like the amount found on the premises. Otherwise you have issues with far broader government regulations that go beyond the scope of this thread to include any bodily consumed or contacted material.
EDIT: And again, for the marijuana enthusiasts, find counter evidence to the studies that show degenerate growth of the hippocampus as a result of marijuana consumption, with it positively correlating to how much one consumes and how early in life one consumes. Until that can be satisfied sufficiently, there is absolutely no reason why it should be wholesale deregulated and cases LIKE THIS will still occur even if made "legal" to consume in specific conditions.