283. In addition to those cases given in the ritual books, Communion under both kinds is permitted for:
a) Priests who are not able to celebrate or concelebrate Mass;
Otherwise, you need to be in some role:
b) the Deacon and others who perform some duty at the Mass;
It’s not entirely clear to me that a bishop or a pastor can bar “others who perform some duty” from Communion under both forms. Though I think that would be an unfortunate exercise in a creeping clericalism among the lay volunteers.
c) members of communities at the Conventual Mass or the “community” Mass, along with seminarians, and all those engaged in a retreat or taking part in a spiritual or pastoral gathering.
The Diocesan Bishop may establish norms for Communion under both kinds for his own diocese, which are also to be observed in churches of religious and at celebrations with small groups. The Diocesan Bishop is also given the faculty to permit Communion under both kinds whenever it may seem appropriate to the Priest to whom a community has been entrusted as its own shepherd, provided that the faithful have been well instructed and that there is no danger of profanation of the Sacrament or of the rite’s becoming difficult because of the large number of participants or for some other cause.
In all that pertains to Communion under both kinds, the Norms for the Distribution and Reception of Holy Communion under Both Kinds in the Dioceses of the United States of America are to be followed (particularly nos. 27-54).
The bishop is responsible for diocesan norms. While this point is not really in dispute, when a bishop has limited lay Communion under both forms, the question is really one of prudence: is this really what is best for the faithful. “Instruction” and “profanation” mentioned after point c) are really a matter of quality control. And it is curious that despite a greater danger of profanation with consecrated altar bread, that Communion from the Cup has come under recent scrutiny, with this reasoning attached. I suspect that future editions of the GIRM (hopefully) will be more well-rounded on this point and a little less shrill.