Exactly how is it constitutional? The Constitution certainly gives the federal government control over the importation of drugs (under Article I, Sec. 8), but I hardly see how that applies to things like the Controlled Substances Act. If federal drug policy is allowed to stand, there is no end to what powers they can take away from the states. In my opinion, that is more detrimental to society than drugs.
The above article points to the Netherlands as an example of the problems of rampant drug use and the conclusions of the author are probably correct, but such problems should be addressed at the state level. Are you comfortable with what the federal government has already done with tobacco? Where do we draw the line in regards to government expansion?
I mentioned twice on this thread, the constitutional and legal aspects of America's drug control policy. I guess you didn't see them. Here they are again, for your benefit.
America's current national drug control policy, is part of the National Drug Control Policy Reauthorization Act of 1998 and is based on the Controlled Substances Act of 1970. There is nothing unconstitutional about this policy. Link here to the CSA of 1970 and link here to the USSC decision, Tobey v. United States, 500 U.S. 160 (1991) that supports the CSA of 1970.
The basic constitutionality of the act is not addressed because it is not even arguable. Congress can legislate under the Commerce Clause. The ONLY issue was one of delegation, can Congress delegate it's legislative authority to an executive-branch agency. Again, under fairly settled law, Congress can so long as it limits the discretion of the agency and provides the overall structure/guidance to the agency in the grant of delegation, and so long as the agency follows established principles of administrative law (due process, review and comment, etc).