Kent, represented by Leonard Boudin of the Emergency Civil Liberties Union,[3] sued in U.S. District Court for declaratory relief.

Kent v. Dulles was the first case in which the U.S. Supreme Court ruled that the right to travel is a part of the "liberty" of which the citizen cannot be deprived without due process of law under the Fifth Amendment.

Six years later, the Court in Aptheker v. Secretary of State[6] found that the law violated First Amendment principles and left unsettled the extent to which this liberty to travel can be curtailed.

It reviewed prior administrative practice, noting that the power of the Secretary of State over the issuance of passports is expressed in broad terms, but long exercised quite narrowly.

It considered wartime measures, citing Korematsu v. United States,[11] for the proposition that the government could exclude citizens from their homes and restrict their freedom of movement only on a showing of "the gravest imminent danger to the public safety".

It found that when that power is delegated, the standards must be adequate to pass scrutiny by the accepted tests, citing Panama Refining Co. v. Ryan,[12] Cantwell v. Connecticut,[13] and Niemotko v. Maryland,[14] and that where activities or enjoyment natural and often necessary to the wellbeing of an American citizen, such as travel, are involved, the Court will construe narrowly all delegated powers that curtail or dilute them.

It faulted the majority's assertion that the passport denials here were beyond the pale of congressional authorization because they do not involve grounds either of allegiance or criminal activity.

It argued that neither of the propositions set out by the majority — (1) that the Secretary's denial of passports in peacetime extended to only two categories of cases, those involving allegiance and those involving criminal activity, and (2) that the Secretary's wartime exercise of his discretion, while admittedly more restrictive, had no relevance to the practice which Congress could have been said to have approved in 1952 — had any validity: the first was contrary to fact, and the second to common sense.

He did not reach any constitutional questions, delegating to the majority's resolution of the authority question, the inability to rule on the constitutional issues raised by petitioners relating to claimed unlawful delegation of legislative power, violation of free speech and association under the First Amendment, and violation of international travel under the Fifth Amendment.