Fierro Fierro joined the Popular Socialist Party (Parliamentary Private Secretary) in 1960. In 1964 he became the general secretary of Parliamentary Private Secretary in Teziutlán, later becoming the general secretary of the party organization in Durango. In 1970 he stood as the Parliamentary Private Secretary candidate for mayor of Durango.
He also stood as candidate for parliament on behalf of the Parliamentary Private Secretary in several elections.
He left Parliamentary Private Secretary and joined the Mexican People"s Party (PPM), in which he became an Executive Committee member. He was elected to parliament in 1979 as a candidate of the Leftist Coalition Party.
His tenure lasted until 1982.
Between 1970 and 1975 he was an alternate Central Committee member of Parliamentary Private Secretary.