Yes, in the same sense that a street drug user could almost be seen as an amateur anaesthesiologist subjecting themselves to a controlled dosage of opioids for medical purposes. But despite that, street drug use and supervised injection at Insite would both have been criminal offenses if not for changes and exemptions made by legal system to allow them. That's precisely what "decriminalization" is, and a large part of this is the idea that drug abuse should be seen as a medical matter rather than a criminal one.