In November 1926 Treves fled into exile, emigrating first to Switzerland and then to France, where he was one of the more frequent collaborators of the weekly journal of the PSLI (the underground successor to the now outlawed PSU), Rinascita socialista.
In November 1926, Treves fled into exile, first traveling to Switzerland and then to France, becoming a frequent contributor to the underground socialist journal, Rinascita socialista, published by the PSLI, the successor organization of the outlawed PSU.