Not any more. That's called a "secondary boycott", and has been illegal in the US since 1959. Before that, it was common for union truckers to refuse to cross a

Not any more. That's called a "secondary boycott", and has been illegal in the US since 1959. Before that, it was common for union truckers to refuse to cross a picket line. When a company's workers went on strike, deliveries by Teamsters stopped. American labor law was written when unions were much stronger. It assumes strong unions and strong employers in conflict, with the NLRB as referee. That hasn't been true in the US for decades now.