After his military duty from 1963 to 1967, reaching the rank of captain, he studied law at Heidelberg University, where he completed his First State Examination in 1971.
From 1980 to 1984, he worked for the Division for UN Affairs (Security Council, General Assembly) at the Federal Foreign Office in Bonn, Germany.
In 1990, back in Bonn, he was appointed Deputy Head of the Division for Near Eastern Affairs at the Federal Foreign Office.
From 1996 to 2003, Kaul was Head of the German delegation in the negotiation process of the Rome Statute of the International Criminal Court.
Kaul was elected as the first German judge of the International Criminal Court in 2003,[3] and then re-elected in 2006 for a second term of nine years.
[2] From 1997, Judge Kaul played a major role in international efforts to criminalize aggressive war-making, together with former US Nuremberg prosecutors Benjamin Ferencz[5] (b.
[8] Judge Kaul was a member of the advisory board of the Global Institute for the Prevention of Aggression (from June 2012).