Gaston and Isabel returned to Brazil on 1 May 1871, just three weeks before the Emperor and Empress embarked on their own tour of Europe. Isabel was appointed regent with full powers to govern Brazil in the Emperor's absence, though prime minister José Paranhos, Viscount of Rio Branco, and Gaston were expected to hold the reins of power in reality. Following the abolition of slavery in the United States, Pedro II was committed to a gradual program of liberation. On 27 September 1871, with the Emperor still abroad, Isabel signed a new anti-slavery act, passed by the Chamber of Deputies. The Law of Free Birth, as it was called, freed all children born of slaves after that date. On Pedro II's return to Brazil in March 1872, Isabel was once again excluded from government, and resumed private life.