 He was first elected at the Chambly—Rouville riding in the 1957 general election.After serving his term in the 23rd Canadian Parliament, L'Heureux was defeated in the 1958 election by Maurice Johnson of the Progressive Conservative Party.L'Heureux returned to Parliament in a 31 May 1971 by-election at the Chambly riding following the death of incumbent Liberal member Bernard Pilon.