He was one of the first 5 Doctors of Law in the history of the Democratic Republic of the Congo from 1960 to 1963 (together with Etienne Tshisekedi, Dede Alexis, Dipumba Barthélémy, Kabeya Joseph Alidor and Tshibangu Crispin) and Betty Hubert (from Cameroon) and Gakwaya Faustin (Rwandan).
[2] His professional career began in 1964 when he was appointed Legal Advisor and Director of the Studies and Documentation Department at the House of Representatives of the Congolese Parliament.
[4] In 1965, he joined a new political party: the Alliance of Congolese Christian Socialists (ASCCO) and managed to be elected national deputy for the electoral district of Kivu.
He then joined the Popular Movement of the Revolution (MPR) until he was hoisted there as a member of the Central Committee and the Political Bureau.
Léon Mamboleo is one of the eminent lawyers who have always defended the cause of DR Congo before international legal bodies.