[11] According to Lynn H. Nicolas in The Rape of Europa, during World War II, Bignou entered into a profit sharing agreement with Martin Fabiani concerning the shipment of "429 paintings, drawing and watercolors by Renoir, 68 Cézannes, 57 Rouaults, 13 Gauguin, and so forth, to a grand total of 635" artworks.
It included the first manuscript of Céline's Voyage au Bout de la Nuit that the writer had sold to the merchant for ten thousand francs and a painting by Renoir, on May 29, 1943.
[19][20][21] In recent years, several artworks that passed through Bignou were discovered to have been looted by Nazis or sold in forced sales or under duress by Jewish collectors during the Holocaust.
[22] In 2013, Group of Trees, 1890, a watercolour by Paul Cézanne, "surfaced" at the National Gallery of Canada in Ottawa with a provenance that experts said required further verification as the British navy had seized it in a cargo of artworks sent by art dealer Fabiani to Bignou.
[23][24] In 2019, the Kunstmuseum in Bern came under scrutiny for Georges F. Keller's donations of artworks by artists like Henri Matisse and Salvador Dalí because of his association with Bignou, who was described as "sulferous" due to his art dealing with Germans during the Nazi occupation of France.