Gustave Henri Ange Hippolyte Rolin-Jaequemyns was a Belgian attorney at law, diplomat and Minister of the Interior (1878-1884) as a member of the Unitarian Liberal Party. Together with the Swiss jurist Gustave Moynier, he founded the Institut de Droit International (Institute of International Law) and became its first Honorary President.
Even though his personal convictions were deeply religious, he is considered anti-clerical because of his staunch defence of the separation of church and state.
Serving as an advisor to King Rama V of Thailand, he played a crucial role in the reformation of that country to modern western standards and was awarded the title Chow Phya Abhai Raja, the highest distinction ever granted to a foreigner.
His reputation as an expert on international law was widely recognized. He became a member of several national academies, for example 1870 in Montreal, 1872 in Madrid, in 1874 in Belgium and 1881 in Constantinople.
In 1877, the University of Edinburgh granted him the title of Doctor Honoris Causa, and later he received the same distinction from the universities of Cambridge, Oxford and Brussels. In 1889 King Leopold II of Belgium appointed him member of the High Council for the independent state of Congo.