After studying law Fischer, earned his PhD in 1984 from the University of Bochum with a thesis on international law and the use of nuclear weapons.
From 1990, he served as member of several diplomatic delegations to conferences and meetings of non-governmental organizations that dealt with the issues of international humanitarian law and humanitarian assistance.
He was also consultant on these issues for the United Nations, the European Union, several national ministries and various organizations such as the International Committee of the Red Cross ( ICRC).
He is served for more than 10 years as director of the Brussels Representation of the Deutsche Gesellschaft für Internationale Zusammenarbeit. Since his retirement he continues to teach as senior professor at the Ruhr-University Bochum.
At Leiden University, he occupies the chair of international humanitarian law, he is also an Adjunct professor at Columbia University (SIPA), New York, as well as Visiting professor at the Vesalius College, Brussels. From 2002 – 2016 he had been president of the European Inter University Centre for Human Rights and Democratisation in Venice.
