His academic training is in constitutional law, but he later pivoted towards the study of politics especially of the Great Lakes region of Africa.
[2] In 1975, while working as a research assistant at the University of Antwerp, Reyntjens was asked to be involved in a project that involved running a law school at the National University of Rwanda, in Butare.
Public Law and Political Evolution, 1916-1973' (Original French: Pouvoir et droit au Rwanda.
[4] After this, his research widened from Rwanda to the Great Lakes Region as a whole - publishing work on Burundi and on the Democratic Republic of Congo.
Outside of academia, Reyntjens has been called as an expert witness in cases relating to the Great Lakes region in the courts of multiple nations, as well as before the International Criminal Court and the International Criminal Tribunal for Rwanda.