New Zealand is preparing to introduce new legislation specifically to address the "whack-a-mole" issue that the article talks about:

http://en.wikipedia.org/wiki/Psychoactive_Substances_Bill

It will basically set up a regulatory regime whereby any recreational drug which can be proven "low risk" can be sold to anyone over the age of 18. Not really all that different from how "regular" pharmaceutical drugs are tested and approved, actually.