In 1902, the hatters’ union has organized most of the hat manufacturers. D.E. Loewe resisted organizing under the union. He preferred to choose his own prices and wages. This way he could undercut the other manufacturers that joined the union.
Well, the union did not take well to this move by Loewe. Instead, they called for a boycott of his items. Meaning they called for people to refuse to buy what he made. This boycott extended to where ever he sold items including different states.
Predictably, Loewe lost money so he brought a lawsuit against the hatters’ union invoking the Sherman Anti-Trust Act. The act said in part that trusts could not restrict trade or commerce across states. The Supreme Court said that unions fell under this act and the Danbury Hatters’ Case violated it.
This blow to the unions made them realize that they needed representatives in congress. The unions organized and petitioned for more rights. Eventually getting what they want in the 1930s.