He completed his primary and secondary education in Laoag City, Ilocos Norte, graduating as the valedictorian of his high school class.
Ditto became the editor-in-chief of the official university newspaper, the Philippine Collegian, and under his leadership, the paper began publishing editorials critical of Marcos and martial law.
From 1985 to 1987, Sarmiento served as the Chief Legal Counsel and Member of the Governing Council of the Lakas ng Bayan (LABAN).
Later that year, he and Manuel Concordia published a book, Ang Demokrasya sa Pilipinas, which led to their arrest on charges of subversion and inciting to sedition.
[2] Upon the assumption to the presidency of Corazon Aquino, following the 1986 People Power Revolution, Sarmiento was appointed to the Board of Directors of San Miguel Corporation, which was then under government sequestration.
In People v. Nazario, 165 SCRA 186, the Court through Sarmiento acknowledged the void for vagueness rule as able to invalidate criminal statutes.
80806, 5 October 1989, 163 SCRA 386, he wrote for the Court that any restraint on the publication of purportedly obscene materials must satisfy the clear and present danger test.
L-81958, 30 June 1988, 178 SCRA 362, Sarmiento's opinion for the Court upheld as a valid police power measure, the Philippine government's right to temporarily ban the deployment abroad of Filipino domestics and household workers.
Sarmiento invoked the diminution of civil liberties during the Marcos administration, writing: The apprehensions in question chronicle in my mind the increasing pattern of arrests and detention in the country without the sanction of a judicial decree.
We set up a popular government, restored its honored institutions, and crafted a democratic constitution that rests on the guideposts of peace and freedom.
Regent to President Benigno S. Aquino III and this renomination remained pending even as Sarmiento died in Prague, Czech Republic on October 3, 2010.
Sarmiento died due to apparent organ failure, while visiting Prague, Czech Republic, was reported in the Philippine media on October 4, 2010.