the first major piece of antitrust legislation was the
Freedom of contract, a principle that undermined a union's collective purpose, would remain an impediment to labor organizing well into the twentieth century and remains a point of contention today. The first major piece of legislation that affected labor unions was the Sherman Antitrust Act of 1890.The law forbade any restraint of commerce across state lines, and courts ruled that union strikes and boycotts were covered by the law.reedom of contract, a principle that undermined a union's collective purpose, would remain an impediment to labor organizing well into the twentieth century and remains a point of contention today. The first major piece of legislation that affected labor unions was the Sherman Antitrust Act of 1890.