Most states are employment “at will” states. Which means you can be fired for any reason or no reason at all so long as it is not an illegal reason. Despite the hysteria over protected classes it is still easy to fire someone especially if they white, male, under 40, Christian, and not disabled.
So I can fire you for alcohol comsumption or for drinking coffee.
Employers are free to restrict many things that are legal and can do many things that people consider “unconstitutional”. If you do not like it you are of course free to quit.
“Most states are employment at will states.”