As a lawyer of the Structural Alternative Legal Assistance for the Grassroots (SALAG), Jefferson handled court cases of farmers, fisherfolk and indigenous peoples in the Philippines. In line with the so-called alternative lawyering concept, Jefferson was not only litigating but also educating people who are involved in the issues for their involvement in the court cases and for their capacity to address other issues that affected them. And to add legal support to the protection of the rights of farmers, fisherfolk and indigenous people, Jefferson was also involved in lobbying for legal reform with civil society coalitions. Jefferson was the Legal Coordinator of SALAG in 1985-1989, and its National Coordinator/President in 1989-1992. Jefferson became the Project Coordinator of Asia and Pacific Regional Resource Center for Human Rights Education (ARRC) in 1992-1995 in Bangkok. From 1995 till present, Jefferson worked for the Asia-Pacific Human Rights Information Center (HURIGHTS OSAKA) based in Osaka.