During the Agartala Conspiracy Case, Hossain prepared the writ petition and worked on the case with Queen's Counsel Thomas William. In 1967, 1968 and 1969, he was elected vice-chairman of the East Pakistan Bar Council (now the Bangladesh Bar Council). Hossain was elected the last vice-chairman of the All-Pakistan Bar Council in 1969. In 1969 and 1970, he was involved in the round-table conferences between the government of Pakistan and major opposition parties led by the Awami League and Sheikh Mujibur Rahman.