During and after World War II (1939–45) he was involved in discussions about France's position in a future European federation.

Paul Bastid attended the École Normale Supérieure, where he passed the agrégation examinations in philosophy and law, and became a Doctor of Letters.

He was made a member of the Académie des Sciences Morales et Politiques and professor of the Faculty of Law of Paris.

[1] At the start of the summer of 1942 Bastid circulated a document to many parliamentarians in which he asserted that Marshal Philippe Pétain had violated the mandate given him on 10 July 1940, and protested against the abuses of the Vichy government.

[6] When the Council drew up its programme for political reform after the Liberation in 1944, Bastid threatened to resign if it committed to granting the vote to women.

In a report issued in April 1943 Bastid was skeptical about a collaborationist vision of Europe along the lines advocated by Vichy.

[11] In August 1944 Bastid occupied the Ministry of Foreign Affairs at the Quai d'Orsay in the name of the CNR, and directed it for several days pending the arrival of the government from Algiers.

[1] Bastid ran for Cantal on the platform of the Radical Socialist Republicans in the elections to the 1st National Constituent Assembly, but was defeated.

[4] In the legislature he was mainly concerned with questions of international relations, including the London Conference, the Council of Europe, ratification of the North Atlantic Treaty, Indochina and German rearmament.

[1] Bastid and other Radical "Europeanists" such as René Mayer, Henri Queuille and Félix Gaillard advocated a pragmatic and gradualistic approach to the European Union.

They hoped to make the European market as open as possible, but did not want to upset Radical opponents of a Federal Europe.

[4] Bastid was a prolific author on subjects that included the law, history, fiction and poetry, and contributed to many journals.