In the case of Michael A. Lebron v. National Railroad Passenger Corporation (Amtrak), 1994, the U.S Supreme Court ruled in favor of Lebron, a political activist who wanted to display his artwork criticizing US policy on Amtrak's billboard at Penn Station but was denied by Amtrak citing its policy against political messages. The court held that although Amtrak is not a government agency per se, it was established and heavily regulated by Congress and therefore must adhere to First Amendment protections for free speech. This decision clarified that entities created by the government for public purposes cannot violate constitutional rights even if they operate in some respects like private businesses.

In the dissenting opinion for Michael A. Lebron v. National Railroad Passenger Corporation, Justice Clarence Thomas, joined by Chief Justice William Rehnquist and Justice Sandra Day O'Connor, argued that Amtrak should not be considered a government entity subject to First Amendment constraints. They contended that while the federal government does have significant control over Amtrak's operations due to its funding and appointment of some board members, this does not make it a governmental body because it also has private interests involved in its management and operation. The dissenters believed that previous court decisions had established more stringent criteria for determining whether an entity is public or private than what was applied in this case. They suggested that treating entities like Amtrak as part of the state could lead to other privately owned corporations being subjected to constitutional restrictions if they receive substantial federal aid or regulation.