In the case of Consolo v. Federal Maritime Commission et al., 1965, the U.S Supreme Court ruled in favor of Consolo, a freight forwarder who was denied due process by the Federal Maritime Commission (FMC). The FMC had revoked his license based on evidence not disclosed to him during proceedings. The court held that administrative agencies like FMC could use evidence obtained outside formal hearings as long as it did not violate statutory requirements or constitutional rights. However, they also stated that an agency's decision cannot be solely based on such undisclosed information and must provide an opportunity for rebuttal. In this case, since Consolo was denied access to certain pieces of evidence used against him and thus unable to challenge them effectively, his right to due process was violated.

In the dissenting opinion for Consolo v. Federal Maritime Commission, Justice Harlan disagreed with the majority's view that an administrative agency can make a decision based on evidence not presented at a hearing and without giving parties involved an opportunity to respond. He argued this violated due process rights under the Fifth Amendment of the Constitution. He also expressed concern about agencies having unchecked power to decide cases based on undisclosed information, which could lead to arbitrary decisions and undermine public confidence in administrative proceedings. Furthermore, he believed that allowing such practices would blur distinctions between adjudicatory and legislative functions of agencies, potentially leading to further constitutional issues.