Castelli won Paroissien's acquittal by invoking the doctrine of the retroversion of the sovereignty of the people, which claimed that the Spanish American lands were a personal possession of the King of Spain but not a Spanish colony. That approach was already old, and it was used to legislate in both districts, but in this context Castelli argued that neither the Council of Regency or any other power of Spain—other than the rightful King—had authority over Spanish America. Castelli said that "the will of the people of Spain is not enough to bring the Indies to obedience". Under these premises, Castelli argued successfully that the regency offered to the sister of the captive king, while not denying the legitimacy of Ferdinand VII, was not an act of treason, but a legitimate political project that should be resolved by the Spanish American people without the intervention of the peninsular Spanish.