The Feds already did their job by making it legal for the states to allow it. Whether homebrewing is allowed in your state is considered a "states" issue and the Federal government does not have any jurisdiction on it.
Yeah, if your state has restrictive liquor laws, that's all on your state. The Feds can't make states allow homebrewing. The Feds have some power in the commerce clause to regulate businesses, for instance to prevent discrimination within a legal business operation (no "whites-only" restaurants.) Since homebrewing isn't commercial, I don't think it falls under commerce clause.
At one point in time, the commerce clause was interpreted pretty broadly. In the case you mention above concerning the whites-only restuarant (Katzenbach v. McClung), the Supreme Court basically said that if Congress can reasonably conclude that, taken in the aggregate, an activity will have a substantial effect on interstate commerce, then it is within Congress' power under the commerce clause to regulate that activity.
It's a stretch, but Congress could conceivably regulate homebrewing under that interpretation. However, the SC has limited the power of Congress under the commerce clause quite a bit since that case was decided.
I don't think that logic regarding the Commerce Clause works since the 21st Amendment gives state govts broad discretion in terms of how they will regulate alcohol. But it does raise a constitutional question about which part of the Constitution is more important.
Bingo. The way congress "regulates" homebrewing in spite of the 21st Amendment is under its power to tax. The bill that President Carter signed making it legal to homebrew was a tax exemption for beer brewed for personal or family use up to 100 gallons per year per adult, or 200 gallons per household.
Say that Congress decided to try to override a state law that made homebrewing illegal, do you think it would be successful in doing so under the commerce clause or would it fail (due to a more restrictive interpretation of that clause, the 21st amendment, or any other reason)?
My gut tells me that under the canon of construction that a specific statute trumps a general one, Congress would lose under a Commerce Clause argument. To me, the 21st Amendment (specific statute) is an exception to the Commerce Clause (general statute), thereby allowing states to regulate what would otherwise be in the exclusive purview of Congress.
Although, some would argue that the 21st Amendment is a truism to the extent that it merely restores to the states the rightful power to regulate alcohol. From that viewpoint, the Commerce Clause would have no bearing on the question since the states' power to regulate alcohol predated the Constitution and alcohol regulation is not an expressly enumerated power.
Now, in the commercial alcohol sphere, there do exist commerce clause issues. They mostly revolve around the dormant commerce clause doctrine. Granholm v. Heald
is probably the most well-known modern case on the subject. Check it out if you'd like to know more about the balance between the 21st Amendment and the dormant commerce clause doctrine -- sounds exhilarating, right!?