Article VI, Section 2 (Supremacy Clause) which says that federal law trumps state law.
The same clause that gives the Feds authority to prohibit medical marijuana when the state has approved it. Nothing new, ellery.
Guess the founders forgot that they were writing on hemp when they outlawed in in that invisible amendment of yours.
Next you'll be telling us the purpose of the Constitution is to limit citizens' rights and enumerate powers for the state.
This Constitution, and the Laws of the United States which shall be made in Pursuance thereof; and all Treaties made, or which shall be made, under the authority of the United States, shall be the supreme Law of the land; and the Judges in every State shall be bound thereby, any Thing in the Constitution or Laws of any State to the Contrary notwithstanding."