This is topical for us here in Kansas City as Bishop Finn has converted a regional spiritual attraction in the city of Saint Joseph to a diocesan-wide event.
59. In processions in which the eucharist is carried through the streets solemnly with singing, especially on the feast of Corpus Christi, the Christian people give public witness to their faith and to their devotion toward this sacrament.
However, it is for the local Ordinary to decide on both the advisability of such processions in today’s conditions and on a place and plan for them that will ensure their being carried out with decorum and without any loss of reverence toward this sacrament.
And again: who decides? Not Rome, and not the parish pastor, but the bishop.