I know that punishing drug dealers is the topic here, but I feel more importantly, in fact I feel it critical that we need to get those addicted some help. Drug use/addiction has risen dramatically and we now have an epidemic. What we've done in the past as far as drug abuse hasn't worked. Cost is one of the main factors of addiction; many addicts don't have health insurance making it virtually impossible for them to go through any sort of rehabilitation program as the cost of successful rehabilitation programs is astronomical. Portugal has had some success:
http://www.cbc.ca/news2/interactives/portugal-heroin-decriminalization/
There is no single solution to the problem, but so long as the drugs are available, the users will find a way to get them, if that means stripping the sluminum siding off your house and selling it for scrap. I know a guy who worked in Singapore, where the dealers are summarily executed. They seem to be having far fewer problems there than we have here, where in virtually any town in the US you can get meth, heroin, etc.
The problem goes far beyond the simple dealing/use of these drugs, but well into everything from armed robbery to turf battles (drive-by shootings) to petit and grand larceny to fund the addicts and the stolen goods and human trafficking rings that pick up those goods.
The question is one of where the weak link is in that chain, what choke point would bring the works grinding to a halt,. and without being able to control the importation or manufacture of the drugs, the dealers are the link which could most likely be broken, if the will is there to make dealing so serious a crime that it is effectively deterred.
Otherwise, play pattycake with the problem by focusing on the users rather than the supply, and you are fighting a battle by going hand to hand with each individual soldier instead of cutting off the supplies that keep the war going and the transport/distribution networks that make the problem possible.
That said, a fair trial, observe the Constitution, get a conviction following due process, and eliminate the critical link in the supply chain once and for all. Not only will there be much lower rates of repeat offenders, others might be deterred from taking up that particular vocation.