Short answer is that, on a very long time horizon, I think drug laws probably are just a phase that will go away. But socially- or religiously-enforced policing of conduct is as old as human culture itself, so even if drugs become decriminalized, the tendency to proclaim some substances or actions "taboo" is unlikely to ever disappear. The specific actions/substances in question can change fairly quickly, however.
Maybe criminalizing religions would be an answer. It is fascinating how perception of drugs changes over time. Even the Dutch royal family had a cocaine manufacturing site last century.
Even if you destroy religion, the underlying drives that created religion in the first place will persist. The religions will just be less recognizable as religion, taking on a more secular flavour. Instead you'll end up with stuff like conspiracy theories, political ideology and pseudo-science taking over.
One of the nice things about science is that its members keep their religion and their scientific work separate. It's particularly noticeable when you look through the history of science. There's a long tradition of secularism that has benefited the religious and the non-religious alike.
Issac Newton, for example, had very unorthodox opinions about God and the Trinity. To become the Lucasian Professor of Mathematics at Cambridge, he needed a get a special exemption from King Charles II, as traditionally the chair had required that you be an ordained Anglican priest. It's that very same exemption that Newton got for his unusual religious views that allowed Stephan Hawking to hold the chair as an atheist.
There are different practices on which different organized religions depend to keep the "count of the believers" steady and their influence strong which could actually be criminalized when there were enough consciousness and willingness (without disallowing individuals believers to believe). But there surely isn't enough willingness, especially not in the US where publicly "non-believing" more or less excludes you from the politics (shouldn't that be changed for the start?) and the religion organizations have the status of the... sacred cows.
Looking back, there were many very good reasons why the religions were not put in the constitution.
Criminalizing religion would be like criminalizing sex. It's a behavioral pattern based on instincts of the majority of the population, furthered by social proof and the political necessity of controlling the populace.
I supposed you could try to create a better religion. Do what thou whilst as the basic creed basically - which, incidentally, is what the church of satan preaches :)
