[rayiner]

The Commerce Clause precludes states from erecting trade barriers between each other. While Congress could in theory do so, (1) it's never to my knowledge ever used its Commerce Clause powers in that way, and (2) provisions like the Privileges and Immunities Clause creates independent prohibitions on erecting barriers between states.

[ashelmire]

Yet... alcohol can not be freely moved between states. There are clearly cases where interstate trade is prohibited.

[rayiner]

There is a narrow exception for public health, e.g. plant quarantine laws. But the usual tools countries use: tariffs, immigration controls, capital controls, etc., are unavailable.