You too can be a smartypants – Why some beers don’t have ABV on the Label, isn’t it illegal?

Not it’s not illegal, actually the opposite. After Prohibition was repealed, Congress passed a law in 1935 that banned the listing of alcohol content on cans and bottles of brew. The thinking was that if the beers prominently listed their alcohol content, it would cause breweries to compete in “strength wars,” attempting to make the strongest beers. The ban on listing alcohol content on beer lasted until 1995 when the Coors Brewing Company successfully challenged the law.
Via Vinepair