A friend of mine in Rome recently had the privilege of assisting in the distribution of Holy Communion at St Peter's and it was made abundantly clear that communion must be given on the tongue. Although I notice that not all those assisting in such a way always follow this injunction (and I'm sure it might be difficult if individuals present their hands in a way that they have grown accustomed to in their own parishes).
What does all this point to? That the Holy Father has realised from past experience that legislation - even from the Holy See - is often ignored at a local level. How often have I heard the cry, "Oh, that doesn't apply here". So, along with legislation he is, I think, trying to change the culture - by encouragement and quiet promotion of a more devout way of doing things.
Let us pray that those most in need will allow themselves to be encouraged.
External Signs of Devotion by the Faithful
Genuflecting and Kneeling Reflect Spiritual Attitude
The Catechism of the Catholic Church reads: "In the liturgy of the New Covenant every liturgical action, especially the celebration of the Eucharist and the sacraments, is an encounter between Christ and the Church" (CCC, No. 1097). Hence, the liturgy is the privileged "place" of a Christian's encounter with God and with him whom he sent, Jesus Christ (cf. John 17:3). In this encounter the initiative, as ever, is the Lord, who presents himself in the heart of the Church, risen and glorious. In fact, "if the figure of Christ does not emerge in the liturgy, who is its principle and is really present to make it valid, we would no longer have the Christian liturgy, completely dependent on the Lord and sustained by his creative presence" (Benedict XVI, To the Bishops of Brazil [North 2], April 15, 2010). Christ precedes the assembly that celebrates. He -- who acts inseparably united to the Holy Spirit -- convokes, gathers and instructs it. Because of this, the community -- and the faithful who take part -- "should prepare [...] to encounter [the] Lord and to become 'a people well disposed.'" (CCC, No. 1098). Through the words, actions and symbols that constitute the scheme of every celebration, the Holy Spirit puts the faithful and ministers in living relationship with Christ, Word and Image of the Father, so that they can insert into their own life the meaning of what they hear, contemplate and carry out. Hence, every "sacramental celebration is a meeting of God's children with their Father, in Christ and the Holy Spirit; this meeting takes the form of a dialogue, through actions and words" (CCC, No. 1153). In this meeting, the human aspect is important, as St. Josemaría Escrivá also pointed out: "I don't have one heart to love God and another to love the people of the earth. With the same heart with which I loved my parents and I love my friends, precisely with this same heart I love Christ and the Father and the Holy Spirit and Mary Most Holy. I will never tire of saying it: We must be very human because, otherwise, we cannot even be divine" ("Christ Is Passing By"). This is why filial trust must characterize our encounter with Christ. Without forgetting, however, that "this familiarity also entails a danger: that the sacred we continually encounter becomes a habit for us. Thus, reverential fear is extinguished. Conditioned by all our habits, we no longer perceive the great, new, amazing fact that he himself is present, speaks to us, gives himself to us" (Benedict XVI, Holy Chrism Mass, March 20, 2008). The liturgy, and in a special way the Eucharist, "is the encounter and unification of persons; the Person, however, who comes to meet us and desires to be united to us is the Son of God" (Benedict XVI, To the Roman Curia, Dec. 22, 2005). The individual and the community must be aware of being before him who is thrice Holy. Hence, the necessary attitude is one full of reverence and of a sense of wonder, which gushes from knowing oneself in the presence of the majesty of God. Was this not perhaps what God intended to express when he ordered Moses to take off his sandals before the burning bush? Was not the attitude of Moses and Elias born from a similar awareness, who did not dare to look at God face to face? And did not the Magi show this same disposition of spirit, who "prostrated, adored him"? The different personages of the Gospel who met Jesus -- he who passes, who forgives -- do they not also give us an exemplary model of conduct for our encounters with the Son of the living God? In reality, physical gestures express and promote "the intention and spiritual attitude of the participants" (General Instruction of the Roman Missal, No. 42), and enable one to overcome the danger that snares every Christian: habit. "For us who have always lived with the Christian concept of God and are accustomed to it, the possession of hope, which comes from the real encounter with this God, is almost no longer perceptible" (Benedict XVI, "Spe Salvi," No. 3). Because of this, "a convincing sign of the effectiveness that the Eucharistic catechesis has on the faithful is surely the growth in them of the sense of the mystery of God present among us. This can be verified through specific manifestations of reverence toward the Eucharist, to which the mystagogic way should introduce the faithful" (Benedict XVI, "Sacramentum Caritatis," No. 65). The acts of devotion are understood in an adequate way in this context of encounter with the Lord, which implies union, "unification [that] can only be realized in keeping with the form of adoration" (Benedict XVI, To the Roman Curia, Dec. 22, 2005). We see in the first place genuflection, which is done "by bending the right knee to the ground, signifies adoration, and therefore it is reserved for the Most Blessed Sacrament, as well as for the Holy Cross from the solemn adoration during the liturgical celebration on Good Friday until the beginning of the Easter Vigil." (General Instruction of the Roman Missal, No. 274). The bowing of the head instead means reverence and honor. In the Creed -- except in the solemnity of Christmas and of the Annunciation (Incarnation), in which it is replaced with genuflection -- we carry out this gesture pronouncing the wonderful words: "By the power of the Holy Spirit he became incarnate from the Virgin Mary, and was made man." Finally, we would light to highlight the gesture of kneeling at the moment of the consecration and, where this use is kept, at Communion. They are strong signs, which manifest the awareness of being before someone special. It is Christ, the Son of the living God, and before him we fall on our knees. In kneeling, the spiritual and physical meaning form a unity, because the bodily gesture implies a spiritual meaning and vice versa, the spiritual act calls for a manifestation, an external translation. To kneel before God is not something that "is not very modern"; on the contrary, it corresponds to the truth of our being itself. "One who learns to believe, also learns to kneel, and a faith and a liturgy that no longer knows about kneeling would be unhealthy in a central point. Where this gesture has been lost, we must learn it again, to remain with our prayer in the communion of the Apostles and martyrs, in the communion of the whole cosmos, in the unity with Jesus Christ himself" (J. Ratzinger, Theology of the Liturgy [Opera Omnia 11]. LEV, Vatican City 2010, p. 183).