Hossain is renowned worldwide as a jurist and enjoys a long-standing association with the United Nations. Between 1998 and 2003, he served as the UN Special Rapporteur on Afghanistan. He served two terms on the UN Compensation Commission in Geneva. In addition, he has appeared in several international arbitrations, both as a lawyer and an arbitrator. He was a member of the Iran-United States Claims Tribunal. He was Co-Chair of the United Nations Commission of Inquiry into Human Rights Violations in the Occupied Territories in 2001. He was Chairman of the Advisory Commission on Human Rights for the Commonwealth Secretariat. He was also a member of a human rights mission to Indonesia concerning the status of East Timor. During the 2006 United Nations Secretary-General selection, Hossain's name was floated as a possible candidate.