In doing so, it rejected an interpretation of the 21st Amendment that granted the states the power to regulate all aspects of alcohol within their borders.
Most small and a goodly number of midsize states wouldn't want to see their relative power diluted, so such an amendment would have little chance of ratification.
Holland (1920), Justice Oliver Wendell Holmes followed this logic to declare that no "invisible radiation from the general terms of the Tenth Amendment" applies to the Treaty Power.