Stabby, I feel sorry for your uncle, and your family, I really do. What some drugs do to the body is absolutely horrible. But the point is your uncle, and people like your uncle get drugs while they are illegal. It doesnt matter what law enforcement does, drugs will always be accessable to anybody who wants them. Go to any town with more than 1000 people in america, and every person thats been living in that town for a while will be able to tell you not only what part of town to go to, but the name of the street. Not only that, but the people who sell these drugs on the street dont care about selling to minors, or selling drugs that may be unsafe (moreso than the drug itself), or if a drug is laced, they just care for the payoff.
All the "war" on drugs does is waste valuable recources when people will do drugs anyway, and this may sound harsh, but your uncle CHOSE to do those drugs, presumably as an adult. If he was young when he started, then he would have had more trouble getting those drugs with a government enforced age limit. Again, I feel do feel sorry for your uncle, even though I dont know him, or you. Im not saying that the government embrace drugs, but regulations would end the violence that has to do with dealing, minimize drug use by minors, and make sure that the drug passes FDA standards. I assume your Uncle contracted AIDS from a dirty needle (you say he was a heroine addict), that is exactly what regulation would prevent.
edit: gotta add, that in this situation I mention, people need to be well informed about the negative affects of these drugs. One thing that really annoys me are the anti-drug campaigns that lie. There are school programs already to inform kids about drugs though (if only our public school system wasnt in the cr@pper).