Gillego succumbed to a stroke while undergoing treatment at the National Kidney Institute in Quezon City.
He was a three-term veteran of the House of Representatives, and served as chairman of the House committee on civil, political and human rights.
He was instrumental in the unmasking of the fake Marcos medals, and was one of the prime movers of the Movement for Free Philippines — made up of Filipinos in exile in the United States who fought Marcos.