Formerly a practicing lawyer, government official, and law teacher, he was the first Puerto Rican appointed to a federal judgeship in the continental United States (1979).

Cabranes moved to The Bronx, New York at the age of 5, when his father, one of Puerto Rico’s first professionally trained social workers, serving as Chief Probation Officer of the U.S. District Court for the District of Puerto Rico, was recruited by the National Council of Jewish Women to serve as Director of Melrose House, a settlement house in the South Bronx that had historically served Jewish newcomers and increasingly devoted its efforts to aid Puerto Ricans who, as United States citizens, were part of a massive migration by air to New York.

José Cabranes graduated from Flushing High School in 1957 and earned a Bachelor of Arts degree in history from Columbia College in 1961.

[5][13][14] Both Senators Daniel Patrick Moynihan of New York and Abraham Ribicoff of Connecticut were reported to have offered to recommend his appointment to President Carter.

[17] Contemporary news accounts reported that in 1993 Cabranes was considered by President Clinton for appointment to the seat on the Supreme Court of the United States that ultimately went to Ruth Bader Ginsburg.

[22] Newspaper accounts in 1994 likewise reported that Cabranes was considered for the vacancy created by the retirement of Justice Harry Blackmun, which ultimately was filled by Stephen Breyer.

[13] On August 9, 2013, Cabranes was designated by the Chief Justice of the United States to a seven-year term as one of the three judges on the Foreign Intelligence Surveillance Court of Review.

2000): Cabranes, writing for the panel in a matter of first appellate impression, held that the district court was without congressionally authorized jurisdiction to try a civilian charged with committing a crime against an individual on a United States military installation abroad.

2001): Cabranes, writing for the panel and granting the government's petition for mandamus, held that the district court misapplied the teachings of Brady v. Maryland, 373 U.S. 83 (1963) and its progeny in holding that the government was required, as a matter of constitutional law, to disclose all impeachment evidence immediately, pursuant to defendants' request for such, without regard to its materiality and far in advance of trial.

denied, 540 U.S. 1051 (2003): Cabranes, writing for the panel, held that the district court erred by finding the Federal Death Penalty Act of 1994 unconstitutional.

Cabranes held that, to the extent that the challenge against the statute relied upon the Eighth Amendment, it was foreclosed by the Supreme Court's decision in Gregg v. Georgia, 428 U.S. 153 (1976).

With respect to the Due Process Clause, Cabranes held that it protected against government infringement upon rights that were so rooted in the traditions and conscience of the people as to be ranked as fundamental, but that the claim that there was a fundamental right to a continued opportunity for exoneration throughout the course of one's natural life was not (as the district court had suggested) a novel issue, and indeed, was foreclosed by relevant Supreme Court precedents.

denied 540 U.S. 933 (2003): Cabranes, writing jointly with other members of the panel, held that the district court erroneously concluded that the acts charged in one of the counts against the defendant were offenses against the law of nations that supported the exercise of universal jurisdiction.

Cabranes concluded that customary international law currently does not provide for the prosecution of "terrorist" acts under the universality principle, in part due to the failure of States to achieve anything like consensus on the definition of terrorism.

Cabranes nonetheless held that prosecution and conviction of the defendant on the count in question was both consistent with and required by the United States' treaty obligations and domestic laws.

§ 1350, is limited to those clear and unambiguous rules by which states universally abide, or to which they accede, out of a sense of legal obligation and mutual concern.

Cabranes concluded that the rights to life and health are insufficiently definite to constitute rules of customary international law and that plaintiffs, who alleged that Peruvian operations of an American mining company had caused severe lung disease, have not submitted evidence sufficient to establish that customary international law prohibits intranational pollution.

2005): Cabranes, writing for the panel, affirmed a district court's dismissal of a suit alleging excessive force on the part of New York police officers.

Cabranes held that, notwithstanding the general rule that district courts may not weigh evidence or assess the credibility of witnesses at the summary judgment stage, a district court may grant summary judgment where a plaintiff relies almost exclusively on his own testimony and that testimony is "so replete with inconsistencies and improbabilities" that no reasonable juror would undertake the suspension of disbelief necessary to credit he allegations made in the complaint.

Cabranes held that Congress did not intend to include prisoner disenfranchisement provisions of the type adopted by New York within the coverage of section 2 of the Voting Rights Act, and that Congress made no clear statement of an intent to modify the federal balance by applying the Voting Rights Act to these provisions.

2007): In a concurring opinion, Cabranes urged the Supreme Court to revisit and clarify its precedents on pleading standards in order to determine whether they strike the right balance between the need to deter unlawful conduct and the dangers of exposing public officials to burdensome litigation.

Ricci v. DeStefano, 530 F.3d 88 (2d Cir 2008): In a dissenting opinion joined by five other members of the 13-member court, Cabranes objected to the perfunctory affirmance of an award of summary judgment to the defendants in a civil rights action.

2008): Affirming the convictions of Al Qaeda terrorists for their involvement in the bombing of the American Embassies in Nairobi, Kenya and Dar es Salaam, Tanzania, Cabranes held, as a matter of first impression, that the Fourth Amendment's warrant requirement does not govern searches of U.S. citizens conducted abroad by U.S. agents; such searches need only satisfy the Fourth Amendment's requirement of reasonableness.

The wiretap applications were submitted and approved as part of a federal investigation of the "Emperor's Club," a prostitution ring linked to the former Governor of New York, Eliot Spitzer.

Notably, Cabranes held that the Due Process Clause did not require the retroactive application of a change in state criminal law.

Cabranes rejected the New York Thruway Authority's argument that its action was not subject to scrutiny under the dormant Commerce Clause because it was a "market participant," and the opinion established that dormant Commerce Clause challenges to highway toll policies must be analyzed under the factors set forth in the Supreme Court's opinion in Northwest Airlines, Inc. v. County of Kent, 510 U.S. 355, 369 (1994).

In time, he became a teacher in the island's capital city and principal of the Rafael M. de Labra School in Santurce, San Juan, Puerto Rico.

He later served as a supervisor of social work in several of the reconstruction programs of the territorial government of the New Deal era (1934–1940), organizing and directing the territory's first program of probation and parole and later, in Mayaguez, serving as director of the Escuela Industrial Para Niños (Industrial School for Boys), one of the first "reform schools" on the island.