The main message he is setting out is that drugs should be a health problem and not a criminal one. I have argued this many times that the way our society acts is one of punishment - taking drugs is bad/immoral/whatever and as such you should be punished. In reality surely it would be much better for society if these people were not handed ridiculous criminal records and instead were given the help that they need (if indeed they need help) to become a productive member of society.
Anyone with a criminal record will find it hard to find employment, or at least as good employment as they could have previously obtained, as such they are not fulfilling their potential and we all lose out. This is a vicious circle as once you hinder someone's chances by giving them a criminal record they are less likely to 'get themselves clean' and more likely to stay on drugs.
A point I hadn't previously raised regarding decriminalisation (or perhaps more appropriate to legalisation) is that by doing so you remove the ability of certain people to get others 'hooked' on a drug and become dependent on that person and as a result a life of crime.
I disagree that the overall aim should be to reduce the number of drugs users (as I don't think that this sort of moral decision should be imposed by anyone), however the aim should be to reduce the harm to each individual and society as a whole, the only way I see this as being possible is to bring people out of the shadows so they can receive any support that they need and for those who don't have a problem to not have their lives ruined by a silly criminal conviction.
Basically it can be summed up on one phrase mentioned below:
"The war on drugs is not working - there needs to be a rethink".
It always pleases me to hear another sensible voice adding their weight to the argument, unfortunately I don't see any changes happening soon!