Luther was elected to the supervisory board of the "Reichsbahn" in the summer of 1926. At the end of 1928 he left, to make room for a representative of the Free State of Prussia. In March 1929, he became a member of the board of directors of the "Gemeinschaftsgruppe deutscher Hypothekenbanken" (association of German mortgage banks). He also joined the DVP. In 1928/29, Luther was also active in the "" and became its founding president in January 1928. The institution worked on a reform of the federal structure of the Reich, notably the problem of the dominant position of Prussia compared to the other "Länder".