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 went into hiding, initially seeking refuge in Switzerland before settling in France, where he became a prominent contributor to the clandestine socialist journal, Rinascita socialista, which was published by the PSLI, the successor organization of the PSU.