 Arroyo participated in the trials of political detainees such as Senator Benigno Aquino, Jr., ABS-CBN Executive Eugenio Lopez, Jr., Cebu politician Sergio Osmeña III, Communist Party of the Philippines founder and University of the Philippines Professor Jose Maria Sison, Senators Jovito Salonga and Eva Kalaw, lawyers Aquilino Pimentel Jr., Renato Tañada, Eduardo Olaguer and many others.Arroyo actively participated in street demonstrations.He was gassed, injured and hospitalized during protest rallies and incarcerated in a military stockade.