Marijuana Consumption Is Illegal on the Federal Level, Yet States

Marijuana consumption is illegal on the federal level, yet states such as Colorado, Washington, Oregon, and Alaska have passed ballot initiatives that allow the commercialization of recreational marijuana. How are these state laws upheld given the supremacy clause of the U.S. Constitution?

A) The executive branch is constitutionally charged with enforcing the laws passed by Congress, although in this case has cited "executive discretion"-a decision to not enforce the federal law and allow states with popularly approved ballot initiative to have recreational marijuana.
B) The supremacy clause does not apply to drug laws. Instead, jurisdiction has been subsumed by the Drug Enforcement Administration, an agency of the executive branch.
C) The ballot initiatives that allow commercialization of recreational marijuana in the four states are pending approval by the Supreme Court.
D) The U.S. Congress has given these states special exemptions to the supremacy clause.
E) The president has used executive orders to limit the reach of the supremacy clause.