I assume you mean "rational, if your goal is to decrease drug use."

If that is the case, one must also consider all of the costs involved in making the drugs illegal, from paying people to enforce their illegality (DEA, border agents, customs inspections), increased burdens on the legal system, and the funding more prisons, the increase in thefts committed by addicts due to the rise in prices, increased burden on medical services (impure drugs are more hazardous to health)...

If your goal is "decrease drug use at all costs," then I question the rationality of the goal.