Rousset was the first person to use the term "Gulag" in the French language, revealing to the French the Soviet system of labour camps. In 1949, learning that while the concentration camps in Nazi Germany had been destroyed, camps still existed in the Soviet Union, he appealed to former inmates of Nazi camps to form a commission to inspect the USSR camps, which became the "International Commission Against Concentrationist Regimes".
For his efforts he was attacked by Pierre Daix[2] in the French communist newspaper Les Lettres Françaises, which accused him of slandering the Soviet Union, forging the texts of the Soviet laws, and spreading misinformation. Rousset brought libel charges against the newspaper, and in 1951 he won the case.
Along with Jean-Paul Sartre, Albert Camus and Gerard Rosenthal, Rousset was a founder of the left-wing Rassemblement démocratique révolutionnaire (Revolutionary Democratic Rally), which called for a European federation on democratic socialist lines.[3]