While the federal government's laws take precedent over state laws by default, there are restrictions and that's where this case hinged. Unfortunately that battle has been pretty much lost.
Again, the late decisions during the New Deal era ended most of the restrictions on federal power within the states. Now many things that should be controlled by the states, like the legal drinking age, has been taken away by the federal government through the blackmail of state aid. Don't want to have a 21 year old limit for drinking, no highway funding, etc. Basically we took away your money but we won't give it back until your state does what we want. Sometimes this works in the favor of my politics, sometimes not, but I regret something was lost in this change.