This humanitarian group was created a half-century ago by an initiative of Archbishop Giovanni Battista Montini -- the future Paul VI -- to help deal with Eastern European refugees who fled communist dictatorships.
The Geneva-based group planned to celebrate its 50th anniversary in New York, but moved the event to Rome after the Sept. 11 attacks. The migration commission´s president is renowned economist Stefano Zamagni.
The Holy Father said: "I wish to invite you to an ever deeper awareness of your mission: to see Christ in every brother and sister in need, to proclaim and defend the dignity of every migrant, every displaced person and every refugee."
"In this way, assistance given will not be considered an alms from the goodness of our heart, but an act of justice due to them," he said.
The Pontiff insisted that this duty of justice is based on "inalienable rights which do not depend on any human power to concede or deny, for they are rights which have their source in God."
"This is a profoundly religious vision which is shared not only by other Christians, but also by many followers of the other great religions of the world," John Paul II said.
The Pope encouraged the Catholic Migration Commission to "search for new modes of ecumenical and interreligious cooperation, which are needed now more than ever."