Some of them are more flexible, and would classify medical marijuana along with taking a prescription drug. If there is a medical need, you are not "abusing" the drug.
However, too many are inflexible with matters like this. You smoke weed, even if on a prescription, you get harassed by the hounders. No matter if it relieves pain from a terminal illness--so what if you are going to ruin your brain and your liver if you are going to die in a couple of weeks either way? Or, suppose someone smokes weed on a prescription, and it actually cures something. Those dingbats would treat this as if it were a "faith healer" or some other "uncanny" healer.
Worse, it always seems those dingbats that are extremists in these matters that are always intruding. Even if the lead hounder sides with the "If it's a prescription, you are not abusing it" side, it only takes one idiot to poke his nose in your business (usually an assistant hounder or lower-ranked hounder, or pio-sneer) to make things miserable while you are on this treatment. You are thus made to feel as if you are being unfaithful, even if the drug (in this case, weed) is what allows you to function at all. And, when you do die, you are made to feel that you have no resurrection hope because you "took drugs". Notably, lead hounders that are more permissive on matters like these are often the ones that burn out, turn apostate, or get stepped on by the hard nose hounders.