社会主義者鎮圧法
After the expiration of the Anti-Socialist Laws in 1890, Kater had close contacts with the opposition political movement "Die Jungen", which was influenced by anarchist ideas. Kater was one of the founders of the "Magdeburger Volksstimme," a social democratic newspaper started soon after the sunset of the Anti-Socialist Laws. The editors of the newspaper included several adherents of "Die Jungen." At the 1891 Social Democratic Party (SPD) congress, Kater voted against the expelling "Die Jungen" movement from the party. Nevertheless, he remained in the party and did not join the new organization formed by "Die Jungen", the Association of Independent Socialists.