Calixto O. Zaldivar is remembered for his courageous solo refusal, in the early months of martial law, to let President Marcos get away with a claim of legitimacy for his 1973 Constitution.
An associate justice of the Supreme Court since 1964, Zaldivar declared that the 1935 Constitution was still in force and that therefore the new basic law had not been validly ratified through the prescribed procedure. But the other justices chose to accept Marcos’ argument that his Proclamation 1102 had the force of law when it announced such ratification by the citizens’ assemblies.
Held under the rule of the gun, a series of barangay assemblies were allegedly conducted all over the country from January 10 to 15, 1973. It supposedly involved gathering the residents of each barangay, and asking them to raise their hands if they approved the new Constitution. Of course the fake plebiscite produced overwhelmingly positive results.
Again in March 1973, Zaldivar issued a second dissenting opinion, this time with Chief Justice Roberto Concepcion, categorically declaring that the new Constitution had not been validly ratified and therefore could not be enforced. But they were not able to convince the other justices.
Zaldivar was one of those rare public officials who served in each of the three (the legislative, then the executive, and finally the judicial) branches of government.
In 1934 he served as elected representative for Antique, and again in 1938 as his province’s representative in the First National Assembly. During World War II, he served as deputy chair of the Civilian Emergency Administration in Antique. Later he served with the Judge Advocate Service of the Armed Forces of the Philippines holding a lieutenant colonel's rank.
He was elected Antique governor in 1951.
Later he was appointed member of the Reparations Commission, which tested his integrity as a public official. Gaining the president's confidence, he was then appointed acting assistant executive secretary, concurrently as reparations commissioner in 1963. One year later, he was appointed acting executive secretary to President Diosdado Macapagal.
Appointed associate justice of the Supreme Court by Macapagal in 1964, Zaldivar distinguished himself further as a man of courage, integrity, and independence, someone “whom money could not buy.” He is remembered for his landmark decisions and opinions upholding the freedom to form associations, religious freedom over contract rights, equal protection of the law, social justice, and the reserved power of the state to safeguard the people’s vital interests.
After his retirement from the court, at the height of the Marcos dictatorship, Zaldivar served as president of the Philippine Organization for Human Rights in 1976-1979.
Chief Justice Concepcion called Zaldivar "a great man…, who had the courage to act in accordance with the dictates of his conscience," who was "firm in his defense of his conviction and the rule of law." President Macapagal said Zaldivar "did not join in delivering a free people to the slaughterhouse of totalitarianism" and was a "gigantic figure in the libertarian struggle of his people."