David F. Musto

About the author: David F. Musto is a professor at the Yale School of Medicine and author of The American Disease: Origins of Narcotic Control.

Marijuana policy should not be decided at the state level. The prohibition of dangerous drugs is an overriding national concern that requires federal-level decision making. While some states are attempting to legalize medical marijuana, there is no conclusive evidence proving that the drug is an effective medicine. If states such as California are allowed to repeal antimarijuana laws, it would weaken the nation's unified stance against drugs.

Are our federal marijuana laws unraveling? There is reason to think so. Early in the 20th century, each state had its own laws controlling habit-forming drugs, unaffected by federal statutes. In 1914, for example...