Bishops are given homework to implement once they return home:
It is desirable that the competent territorial ecclesiastical authority mentioned in Art. 22, 2, set up a liturgical commission, to be assisted by experts in liturgical science, sacred music, art and pastoral practice. So far as possible the commission should be aided by some kind of Institute for Pastoral Liturgy, consisting of persons who are eminent in these matters, and including laymen as circumstances suggest. Under the direction of the above-mentioned territorial ecclesiastical authority the commission is to regulate pastoral-liturgical action throughout the territory, and to promote studies and necessary experiments whenever there is question of adaptations to be proposed to the Apostolic See.
Above are a few bits of interest. The Institute is recommended as an advisory body for a commission, which itself is responsible for regulation of the liturgy. In effect, this function passes to diocesan directors of liturgy–in places that have them. The question of “studies” and “experiments” is raised. This is the purview of commissions, and it might be interpreted that ICEL was such a group, though I think this passage leans toward regional or dicoesan commissions and “institutes.” So much for the flimsy argument against ICEL that they overstepped their authority by suggesting changes to their bishops and to Rome.