Appointed to the People's Council "Volksraad" in 1927 to represent the constituents in Minahasa, Ratulangi continued to agitate for equal rights and advocating Indonesian nationalism by aligning himself with the Nationalist Caucus ("Fraksi Kebangsaan") that was started by Mohammad Husni Thamrin. He was a co-sponsor of the Soetardjo Petition, which expressed the desire for an independent state through gradual reforms within a ten year period. The petition passed the "Volksraad", but was not accepted by the colonial government. This response to the petition led to the formation of GAPI (described earlier). Ratulangi was not hesitant to criticize the authorities and would eventually be considered a risk to them. He continued to serve in the "Volksraad" until 1937, when he was arrested due to his increasing political views. He was jailed for several months in Sukamiskin in Bandung.