The Supremacy Clause states that the laws passed by the Supreme Court or by the U.S. Congress supersede any law that is passed by a State. In other words, no State can pass a law which would violate a law passed by Congress or violate the U.S. Constitution.

if Federal Law states that no citizen can possess, sell, or use marijuana, why is it possible in States like Colorado, Washington, Oregon and California that citizens can legally possess, sell, or use marijuana? Under Federal Law, the government has the right to shut down these businesses, but they have not.

The question to be determined is "Is it the State's right to permit the sale of marijuana if its citizens have passed a law in that State authorizing such sales even though such action violates a Federal Law?"

does the failure of the Federal Government to take any action against these States indicates that the Federal Government tacitly approved the States actions?