[The Congress shall have Power] To
regulate Commerce with foreign Nations,
and among the several States, and with
the Indian Tribes;
I.e. not that the Federal government must regulate interstate commerce, merely that it has the power to do that, and even if it said that the commerce must be regulated it could still be regulated to the effect that you couldn't e.g. sell across state lines.But yes, the reason the regulation is different for alcohol than for other goods is ostensibly the 21st.