From one of the legal papers, here's as summary of the issue as pending at the
US Supreme Court: "The wine dispute pits the Constitution's commerce clause,
which gives Congress the power to regulate interstate commerce, against the
21st Amendment. That amendment ended Prohibition in 1933 and gave states
considerable power to regulate the transport of alcoholic beverages.

The court, in granting review in the wine cases, consolidated them and asked
parties to confine their arguments to the following question: €œDoes a state's
regulatory scheme that permits in-state wineries directly to ship alcohol to
consumers but restricts the ability of out-of-state wineries to do so violate
the dormant commerce clause in light of Sec. 2 of the 21st Amendment?€� The
dormant commerce clause doctrine generally prohibits state actions affecting
interstate commerce, unless Congress has affirmatively authorized states to
regulate a given area."

Not an easy question, esp. since this court has been very protective of states
rights as well often recognizing the dormant commerce clause.