(2)No licensed wholesale or retail vendors of potable foreign liquor shall reduce the strength of such liquor whether by the addition of water, or by mixing with liquor of a lower strength, or by any other means whatsoever, unless he holds a special licence unauthorising him to do so :Provided that his prohibition shall not extend to the admixture or beer or spirits, as the case may be, of different strength by a licensed brewer or distiller in so far as such admixture is permitted by the rules made for the regulation of breweries or distilleries.
