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 (emboldening and underlining added by me)The GIRM goes on to the reference the Norms for the Distribution and Reception of Holy Communion under Both Kinds in the Dioceses of the United States of America, which, in turn, cites the GIRM to the effect "that the diocesan Bishop may lay down norms for the distribution of Communion under both kinds for his own diocese, which must be observed" (par. 24).
While I fully respect and make no judgment concerning the recent highly publicized decisions by the bishops of Phoenix, Arizona and Madison, Wisconsin to restrict communion under both kinds for the lay faithful of their dioceses, it seems false to argue that this is something that must be done, or that Church teaching unequivocally demands such a restriction when it clearly does not. Individual bishops are certainly free to establish such norms within their own jurisdictions. I think for the sake of unity we have be careful about erroneously claiming to be doing things "right" with the unavoidable implication that those dioceses who continue to regularly offer Communion under both kinds are doing it "wrong" and so are not in conformity with Church teaching.
Both the GIRM and the USCCB’s Norms establish that the faithful should be well-catechized about the Eucharist. In number 25 of the Norms for Distribution, it is established that prior to Communion being offered to everyone under both kinds “and also whenever the opportunity for instruction is present, the faithful should be properly catechized on the following matters in the light of the teaching and directives of the General Instruction:
a. the ecclesial nature of the Eucharist as the common possession of the whole Church;
b. the Eucharist as the memorial of Christ's sacrifice, his death and resurrection, and as the sacred banquet;
c. the real presence of Christ in the eucharistic elements, whole and entire--in each element of consecrated bread and wine (the doctrine of concomitance);
d. the kinds of reverence due at all times to the sacrament, whether within the eucharistic Liturgy or outside the celebration; and
e. the role that ordinary and, if necessary, extraordinary ministers of the Eucharist are assigned in the eucharistic assembly."
It seems to me that a. is sufficient justification for offering Communion under both kinds to all the baptized.
While we're on the subject of the far-reaching and much needed reforms that happened as a result of the Second Vatican Council, today marks the forty-ninth anniversary of the opening of that great event by Bl. John XXIII. It is also the liturgical memorial of Blessed Pope John. Bill Ditewig has a great post on this event, which, at least in my opinion, is too little remarked upon: What a Day! Pope John XXIII and Vatican II!. Dr. Ditewig also posted something wonderful about John XXIII, at whose tomb he remembered the diaconal community of my diocese as we were gathered together for a retreat, from his recent visit to Rome: Reflections on Buon Papa Giovanni.
I also encourage one an all read, or re-read, the address given by Good Pope John XXIII to open this grand council