After studying law and becoming a lawyer, Cocq began his political career in Ixelles, where he was founder of the local Ligue wallonne. He was elected as member of the local council in 1890 and served as alderman, 1900-1919, and then as mayor, 1919-1921.
From 1909 to 1936 he also sat in the Chamber of Representatives as a Liberal member for Brussels, serving as deputy speaker 1930–1931. He became Minister of Justice in the government of Jules Renkin, which took office on 6 June 1931. The government fell in October the following year, leading to the early 1932 Belgian general election.
- 1932: knight grand Cross in the Order of the Crown.
- Chantal Kesteloot (ed.), Au nom de la Wallonie et de Bruxelles français: les origines du FDF (2004), p. 262. (On Google Books).
- M. Epstein (ed.), The Statesman's Year-Book (London, 1932), p. 678. (On Google Books).
- Pol Defosse, Dictionnaire historique de la laïcité en Belgique (Brussels, 2005), p. 64.