§1. It is above all for the entire college of bishops and the Apostolic See to foster and direct among Catholics the ecumenical movement whose purpose is the restoration among all Christians of the unity which the Church is bound to promote by the will of Christ.
§2. It is likewise for the bishops and, according to the norm of law, the conferences of bishops to promote this same unity and to impart practical norms according to the various needs and opportunities of the circumstances; they are to be attentive to the prescripts issued by the supreme authority of the Church.
Source: Code of Canon Law (Vatican.va)