Prior to his doctorate, Yusuf completed post-graduate studies in international law at the University of Florence in Italy.
Yusuf's previous positions include: Legal Adviser and Director of the Office of International Standards and Legal Affairs for UNESCO from March 2001 to January 2009, Legal Advisor (1994–1998) and Assistant Director General for African Affairs, United Nations Industrial Development Organization (UNIDO), Vienna (1998–2001), Representative and Head of the New York office of the United Nations Conference on Trade and Development (UNCTAD) (1992–1994) and Chief of the Legal Policies Service of UNCTAD (1987–1992), Lecturer in law at the Somali National University (1974–1981) and at the University of Geneva (1981–1983), and Somali delegate to the Third United Nations Conference on the Law of the Sea (1975–1980).
He has also been guest professor and lecturer at a number of universities and institutes in Switzerland, Italy, Greece and France.
In 2011, Yusuf would later gain a seat in the advisory council of The Hague Institute for Global Justice.
He became the third African to hold the title after Nigeria's Taslim Olawale Elias (1982-1985) and Algeria's Mohamed Bedjaoui (1994-1997).