From 1917 to 1920, Vileišis participated in the work of the Council of Lithuania. He was the only member to oppose the Declaration of Independence of December 11, 1917, in which Lithuania promised to be Germany's satellite. Vileišis was one of the four members of the Council to resign on January 26, 1918, on the grounds that the Council of Lithuania had no right to usurp the rights of the Constituent Assembly of Lithuania, and that its authority only applied to the determination of Lithuania's future and model of the state. All twenty members of the Council voted on February 16 to the new edition brought by four members (Jonas Vileišis, Mykolas Biržiška, Steponas Kairys and Stanisław Narutowicz), that returned with new edition of Act of Independence of Lithuania. A few days afterward, together with Justinas Staugaitis and Jurgis Šaulys, he left for Germany to seek recognition of Lithuanian independence.