I disagree. I haven't personally read the federal law governing homebrewing, but when state laws are inconsistent with federal laws, the state law is preempted and held invalid. See generally Arbitration and the Federal Arbitration Act, Abortion, etc.
Not knowing the text of the federal law, I'd say there is a possibility that states may somewhat regulate homebrewing, but there is no way they could ban it altogether.
You can also think of it in the opposite. Recently in Gonzales v. Raich the US Supreme Court invalidated state's medical marijuana law because it was inconsistent with the federal drug laws. The court also applied a very broad interpretation of the commerce clause power of Congress in doing so (aggregation principle), which I would try to apply in arguing a state couldn't try to regulate homebrewing within a state even if all of the goods came from within the state and therefore did not affect interstate commerce (which you wouldn't need to do since most likely the goods came from outside the state).
Sorry for the disertation. Stupid state laws piss me off sometimes. I'm thinking of filing suit against my state to invalidate our recently passed stupid keg registration law, so I'm all worked up on this stuff lately.