Can the faithful legitimately received Holy Communion kneeling?
Yes. Here is a letter from the Congregation for Divine Worship responding to this question on 2/26/03:
Prot. N. 47/03/L
This Congregation for Divine Worship and the Discipline of the Sacraments has received your letter dated 1 December 2002, related to the application of the norms approved by the Conference of Bishops of the United States of America, with the subsequent recognitio of this Congegation, as regards the question of the posture for receiving Holy Communion.
As the authority by virtue of whose recognitio the norm in question has attained the force of law, this Dicastery is competent to specify the manner in which the norm is to be understood for the sake of a proper application. Having received more than a few letters regarding this matter from different locations in the United States of America, the Congregation wishes to ensure that its position on the matter is clear.
To this end, it is perhaps useful to respond to your inquiry by repeating the content of a letter that the Congregation recently addressed to a Bishop in the United States of America from whose Diocese a number of pertinent letters had been received. The letter states: "...while this Congregation gave the recognitio to the norm desired by the Bishops' Conference of your country that people stand for Holy Communion, this was done on the condition that communicants who choose to kneel are not to be denied Holy Communion on these grounds. Indeed, the faithful should not be imposed upon nor accused of disobedience and of acting illicitly when they kneel to receive Holy Communion."
This Dicastery hopes that the citation given here will provide an adequate answer to your letter. At the same time, please be assured that the Congregation remains ready to be of assistance if you should need to contact it again.
With every prayerful good wish, I am,
Sincerely yours in Christ,
Mons. Mario Marini