What is copperweld doctrine?

The Copperweld doctrine is a legal principle established by the United States Supreme Court in 1984 that holds that a corporation and its wholly-owned subsidiaries are a single entity and therefore cannot conspire with one another in violation of antitrust laws. The doctrine was established in the case Copperweld Corp. v. Independence Tube Corp. where Copperweld, a steel manufacturer, was accused of antitrust violations for fixing prices with its subsidiary, Independence Tube, a steel tubing manufacturer. The Court ruled that because the two companies were so closely intertwined, they should be treated as a single entity and therefore could not conspire against each other. The Copperweld doctrine has been influential in shaping antitrust law in the United States and has been extended to other areas of law, including labor and employment law.