At the beginning of the Spanish Civil War, in July 1936, he was secretary of the Madrid CNT. He was part of the juries of the so-called «Popular Courts», created after the Cárcel Modelo massacre. Nuño would have been in favor of the "walk" undertaken by the anarchist groups during the first weeks of the war, arguing that "expeditious justice strengthened the revolutionary morale of the people and engaged them in the struggle to life or death that we had engaged.” As Felipe Sandoval would later state, Amor Nuño would have had almost total control over the Madrid Checa.