He first engaged in private practice at the Jose W. Diokno Law Office in 1968, and then he joined the government, working as Technical Assistant (1969–1973) and Associate Attorney (1974–1975) at the Supreme Court, supervised by then Chief Justice Fred Ruiz Castro.

From 1988 to 1990, he worked as legal consultant for the presidential committee on the nuclear power plant under the late Justice Secretary Sedfrey Ordoñez.

Later, he worked as counsel for the Equitable Banking Corporation and its officers and branch managers during the impeachment trial of former President Joseph E. Estrada.

Prior to his retirement, he penned the High Court's ruling in Disini v. Secretary of Justice on the contentious Cybercrime Prevention Act of 2012, a landmark decision.

He conducted a seminar and workshop in legal writing and research in 2007 for the attorneys and investigators of the Office of the Ombudsman upon the invitation of the Philippine Judicial Academy, the United States Agency for International Development, the Rule of Law Effectiveness, and CD Technologies Asia, Inc.