Federal Commerce Power and State Marijuana Legalization

With regards to Article I, Section 8 power to "regulate commerce among the several states" in the constitution... The ability for the Federal Government to regulate Marijuana, similar to Wickard vs Filburn and Wheat, is because Marijuana could be transported across state lines for re-sale thus allowing the Federal government to regulate the growing of Marijuana.

However, in Nevada for example, an individual has already purchased the Marijuana, paid state tax on that Marijuana and has a state recognized legal receipt of that Marijuana.

The question is, does the Federal Government have a case against that individual? The individual has already purchased the goods for personal consumption: not resale. They aren't growing it or manufacturing it. It's the state itself that is in the act of growing/supporting the growing of marijuana and thus enabling the potential transportation of that good across state lines. So, shouldn't the Federal Government be going after the manufacturers: not the purchaser in this case?

Or, putting it another way, could the Federal government have taken the Wheat from me that I had already purchased from Filburn, in the same state, even after I've paid sales tax and have a legal receipt backed by the state?

Does Article I, Section 8 really give the power to the Federal government to regulate Marijuana consumption at the individual level? It seems like all rulings via Article I, Section 8 are with regards to the manufacturing of goods: not individual consumption.