[1] It held that a parent company is incapable of conspiring with its wholly owned subsidiary for purposes of Section 1 of the Sherman Act because they cannot be considered separate economic entities.

[2] Independence Tube commenced a civil action under Section 1 of the Sherman Act against Copperweld Corporation, its wholly owned subsidiary (" Regal Tube Corporation"), and a third-party company that supplied mill ("Yoder Company").

[3] The Supreme Court, in an opinion by Chief Justice Burger and joined by Justices Blackmun, Powell, Rehnquist and O'Connor, held that an agreement between a wholly owned subsidiary and a parent did not fall under the definition of an "agreement" in Section 1 of the Sherman Act because the two companies, while legally separate, constituted a single economic entity.

Because the Sherman Act does not prohibit unreasonable restraints of trade as such - but only restraints effected by a contract, combination, or conspiracy - it leaves untouched a single firm's anticompetitive conduct (short of threatened monopolization) that may be indistinguishable in economic effect from the conduct of two firms subject to § 1 liability.

In American Needle, Inc. v. National Football League, 560 U.S. 183 (2010), the Court refined the rule in Copperweld, holding that intra-enterprise agreements may be reviewed under §1 of the Sherman Act where they deprive the marketplace of independent centers of decision making, thus harming actual or potential competition.