Outside the NCWC, Higgins took part in numerous activities to promote and inform on Catholic social thought. He was elevated to Papal Chamberlain with the title of Monsignor in 1953, and was named a Domestic Prelate in 1959. Upon the advent of the Vatican II Council, Higgins used his experience and knowledge for the Preparatory Commission on the Lay Apostolate and as a Consultant to the Council. He attended all four sessions of the council, 1962-1965. He was on the drafting commission for its document on the laity, the first U.S. priest to receive such an appointment.
Higgins was a champion of human rights and economic justice, especially farm labor where he was the moving force in the Church's support for Cesar Chavez and his union movement. He served in several committees, including the Bishops' Committee for Catholic-Jewish Relations, the Bishops' Committee on Farm Labor, Chairman of the United Auto Workers Public Review Board, member of the American Arbitration Association, Executive Committee member of the Leadership Conference on Civil Rights, member of the Board of the Martin Luther King, Jr. Fund of the United Farm Workers, and Advisor to the Chairman of the U.S. Delegation to the Belgrade Conference on Human Rights. In addition to these activities, Higgins wrote numerous book reviews and articles for many publications, particularly Commonweal and America.
On August 9, 2000, at a White House ceremony, President Bill Clinton honored Msgr. Higgins with the Presidential Medal of Freedom, the nation's highest civilian honor. Msgr. Higgins was selected because of his nearly 50 years of service to the cause of justice for workers and his widespread recognition as the "labor priest" and point man for the American Catholic Church in this regard. He was honored with the University of Notre Dame's Laetare Medal in 2001 and died on May Day, 2002, after a long illness. He was widely mourned as a tireless champion of the labor movement and a progressive voice in the Roman Catholic Church.