As a libertarian, of course, I just want to see drugs legalized. So I'm something of a bystander to the argument between liberals and conservatives over the relative benefits of spending money on treatment programs, and spending it on prisons.
On the other hand, prison doesn't really seem to do a good job of curing drug habits, and it also really screws up the lives of the people we sent there. It's almost . . . why, it's almost as if the libertarians were right all along!
One thing I wonder is how much law enforcement favors drug laws for themselves, or whether they view them as a way to catch bad guys who are otherwise untouchable. I think most people who favor criminalization genuinely mostly want to protect their children from the possibility of acquiring a drug habit--and don't much think about the price that poor kids, and their neighborhoods, end up paying for the laws that send the seller to prison and the user to treatment. But I'm not sure that's how the professionals who support these laws view it, because they're presumably all too aware of how abysmally the laws fail to protect many peoples' kids. I have spoken to three narcotics cops in my life; all three favored legalization, on the grounds that it was simply not possible to make any serious dent in the supply of drugs.
I wonder if instead these aren't the modern way of "getting Al Capone for tax evasion"--a convenient way to throw gangsters in the pokey for other crimes. It is presumably easier to trace the transshipment of large quantities of cocaine back to the kingpin than the murder of one of his underlings. If you believe--and I have heard quite plausible arguments that it is so--that the gangsters at the top are predators who settled on drugs as the most lucrative area for predation, rather than a product of the black market, than this is not entirely unreasonable.
I still think that it would not make sense to criminalize drugs. I'm against "Getting Al Capone for tax evasion", and especially against the notion that we should create special laws to do so. And it seems perfectly obvious to me that the ancillary human costs of these particular laws would be far too high even if I supported them in principle. But it does suggest that libertarian arguments to the drug enforcement community may be addressing the wrong question: we're offering devastating arguments to refute the notion that drug users are bad, or at least bad in a sense that can be justly or even usefully cured by prison. If what they're asking is "Do these laws help me catch bad guys?" then our answers aren't really germane.