The Supreme Court ruled that the right to travel was part of the liberty guaranteed by the due process clause of the Fifth Amendment and that Congress had not authorized the secretary of state to deny passports because of beliefs or political affiliations.
In 1948 the Department of State established a policy of not issuing passports to communists, communist sympathizers, or individuals considered security risks. When Rockwell Kent was denied a passport, he argued that the policy was unconstitutional. Speaking for a 5-4 majority, Justice William O. Douglas
Aptheker v. Secretary of State
Shapiro v. Thompson
Travel, right to