I have often been baffled by the seeming variations in the way the Holy Mass is celebrated in different churches and by different priests. Being a lawyer myself, I have wondered if Church Law did not regulate this very public and doubtless important ceremony. My legal mind tells me that in the same way that the State enforces certain procedures in the public domain—e.g., traffic rules, labor laws, industrial laws, banking laws—the Church as a community of believers must have laws regarding public worship and sacraments. Can you please explain this to me?
Sacred Liturgy and Liturgical Actions
Vatican II affirmed that it is through the liturgy or the public worship of the Church that “the work of our redemption is exercised” and that the liturgy is “the outstanding means by which the faithful can express in their lives and manifest to others the mystery of Christ and the real nature of the Church” (Sacrosanctum Concilium, n.2). Therefore, the Council concludes, “the liturgy is the summit toward which the activity of the Church is directed; at the same time it is the fountain from which all her powers flow” (SC, n.10).
What is liturgy? The Code of Canon Law gives the following definition:
Can. 834, §1. The Church fulfills its office of sanctifying in a special way in the sacred liturgy, which is indeed the exercise of the priestly office of Jesus Christ; in it through sensible signs the sanctification of humankind is signified and effected in a manner proper to each of the signs and the whole of the public worship of God is carried on by the mystical Body of Jesus Christ, that is, by the Head and the members.
§2. This worship takes place when it is carried out in the name of the Church by persons lawfully deputed and through acts approved by the authority of the Church.
From the above, the following essential elements of a liturgical action can be deduced, the last three of which can be classified as veritable canonical requirements:
1) An exercise of the priestly office of Jesus Christ—which is a fundamental element of the liturgy. Thus, when a priest consecrates the Eucharist, Christ is present in the person of the minister; when the confessor absolves, it is Christ who forgives sins; when a faithful baptizes, it is Christ who baptizes.
2) The use of sensible signs, which both signify and effect the sanctification of mankind. In this regard, it is important to comment that the liturgical sign should keep close relation with the sanctification that it signifies (to the exclusion of the vulgar and the inane).
3) The public worship of God is carried out by the whole Mystical Body—i.e., it is offered in the name of the Church. Thus, c.837, §1 states: Liturgical actions are not private actions but celebrations of the Church itself, which is “the sacrament of unity”…therefore liturgical actions pertain to the whole body of the Church and manifest and affect it….
4) The actions are approved by the authority of the Church. Thus, c.846 explicitly establishes: §1. The liturgical books approved by the competent authority are to be faithfully observed in the celebration of the sacraments; therefore no one on personal authority may add, remove or change anything in them.
§2. The ministers are to celebrate the sacraments according to their own rite.
5) The actions are carried out by persons lawfully deputed—a deputation that is different, as previously mentioned, from that enjoyed by all the faithful by virtue of baptism, which is a sharing in the common priesthood mentioned in c.836 and described by Vatican II.
Canon Law and Sacred Liturgy
Is there a Place for Liturgical Norms in Canon Law?
The greater systematic autonomy given to liturgico-sacramental norms in the present Code shows, on the one hand, the deeper understanding of the munera Ecclesiae as a reflection and participation in the munera Christi. In effect, the munus docendi (teaching office of the Church) and the munus sanctificandi (sanctifying office of the Church) are the two great functions of the Church, at the service of which is the munus regendi (the governing office). In effect, such a systematic emphasis on the canonical discipline of sacred liturgy shows an acknowledgment of the insufficiency of the proclamation of the Word of God alone. The Church also has the fundamental mission of carrying out the salvation that it proclaims “through the sacrifice and the sacraments around which revolves the whole liturgical life” (SC, 6).
On the other hand, in contrast to the Code of 1917 which separated worship from sacramental activity, the present Code starts from the doctrinal principle that liturgy—at the center of which are the sacraments—is simultaneously an act of worship and an act of sanctification: through it “God is perfectly glorified and men are sanctified” (SC, 7).
Finally, a recent Instruction from the Congregation for Divine Worship points out that the finality of the liturgical norm is not only to avoid errors, but above all and precisely to unify efforts in the transmission of the truth. In this regard, the liturgical norm finds its reason in the double quality of any liturgical act—i.e., they are public (of the community, of the Church), and they express the faith.
Is there a Liturgical Law?
We have to distinguish between two phenomena:
a) Ritual or Ceremonial Law (ius in re liturgica), which deals with properly liturgical norms—i.e., those whose object is the carrying out of what is signified by the liturgical acts and making them more dignified and fruitful. This includes everything relative to the rites and ceremonies with which the liturgy is celebrated, the contents of Ordos, Rituals and other liturgical books. The liturgy and the sacraments have always enjoyed a certain systematic normative autonomy at the margin of the CIC. Thus c.2 declares: For the most part the Code does not define the rites which are to be observed in celebrating liturgical actions. For this reason current liturgical norms retain their force unless a given liturgical norm is contrary to the canons of the Code.
b) Liturgical Law (ius de re liturgica), which deals with the validity of liturgical acts and the juridic capacity to act of the different subjects. In other words, it deals with the canonical discipline (i.e., contained in the CIC) insofar as it affects liturgical and sacramental acts and other acts of cult.
Summary of Liturgical Law
Liturgical actions are not private actions but are celebrations of the whole Church—i.e., the People of God united and ordered under the guidance of the bishops. This public character of liturgical actions, as well as their intimate connection with the principles of the Faith, constitute the ratio legis on which is based the exclusive competence of the ecclesiastical authority in the regulation of all matters regarding the liturgy. Thus, the whole of liturgical law can be summarized in the following principles:
1) Principle of Substantial Unity. This is premised on the distinction between changeable and unchangeable (immutable) elements of the liturgy: immutable elements are those which depend on the foundational will of Christ—e.g., the substance of the sacraments and whatever is more directly related to that substance; changeable elements are those which do not belong or are not directly related to the substance of the sacraments. The principle is enunciated as follows: “By virtue of it pastoral authority, [the Church] can ordain what may be useful for the good of the faithful, according to the circumstances, times and places. But it does not have any power to change what pertains to the will of Christ, which is what constitutes the immutable part of the Liturgy.” 
2) Principle of Centralization. This reinforces the previous principle, and is contained in c.838:
—§1. The supervision of the sacred liturgy depends solely on the authority of the Church, which resides in the Apostolic See and, in accord with the law, the diocesan bishop (c.838, §1).
—§2. It is for the Apostolic See to order the sacred liturgy of the universal Church, to publish the liturgical books, to review their translations into the vernacular languages and to see that liturgical ordinances are faithfully observed everywhere.
Thus, the following are reserved to the Holy See:
1º All that refers to the validity of the sacraments (c.841).
2º All that refers to the licitud of the sacraments the regulation of which the Holy See has not decentralized to the Episcopal Conferences and to the diocesan Bishops.
3º The edition of liturgical books (c.383, 2).
4º Recognition of versions of liturgical books in the vernacular (c.383, 2).
5º Vigilance over the fulfillment of the universal liturgical norms everywhere (c.383, 2).
3) Principle of Liturgical Elasticity: Inculturation. A complementary principle underlies the fact that the rituals in force do not impose uniformity, but rather permits the use of different forms for celebrating, which are expressions of the richness of the liturgy of the Church. They are at the service of the pastoral function of the liturgy of stimulating and increasing the sense of Christ among the faithful (cf. IGMR, n.313). A particular application of this principle is what has come to be known as inculturation—i.e., the incidence of the different cultures of peoples in whatever is fitting to better express the inexhaustible riches of Christ, provided that it is compatible with the Gospel and does not contradict ecclesial communion.
A different matter is the exaggerated adaptation of the liturgical norms to more specific and even simply personal circumstances—e.g., not to wear all the vestments for Mass on a warm day—under the guise of a misunderstood principle of contextualization. The Holy See has outlawed such “experimentation, unless it counts with the expressed authorization of the Holy See”.
5) Principle of Decentralization. The ecclesiology of Vatican II, which re-emphasized the particular Churches and the dignity of the diocesan Bishops, opened a wide margin for Particular Law in the matter of liturgy. Thus, after establishing the aforementioned principles, the rest of c.838 enumerates the different competencies, corresponding to the need for a certain plurality of liturgical forms, in accordance with the different mentalities and traditions of different peoples (cf. SC, 37-39). This is channeled through:
a) Primarily the Episcopal Conferences: It pertains to the conferences of bishops to prepare translations of the liturgical books into the vernacular languages, with the appropriate adaptations within the limits defined in the liturgical books themselves, and to publish them with the prior review by the Holy See (c.838, §3). The Instruction Varietates legitimae gave further indications on the ambit of this power of the Episcopal Conference and the procedure for its exercise (nn.55 & 66-67).
b) Secondarily the Diocesan Bishop: It pertains to the diocesan bishop in the church entrusted to him, within the limits of his competence, to issue liturgical norms by which all are bound.(c.838, §4).
6) Principle of Full and Active Participation of the Faithful. Of less juridic impact than the foregoing principles is one which is latent in the whole liturgical renewal ushered in by Vatican II, and that is the desire for the full and active participation of all the faithful in the liturgy, each one according to his state and condition.
 SCDW, Varietates legitimae (25.I.1994), n.2: in AAS, 87 (1995), 288-314; L’Osservatore Romano, 30.III.1994; Monitor Ecclesiasticus, 121 (1996), 141-158; Ecclesia, 54 (1994), 1056-1066; Notitiae, 30 (1994).
 SCDW, Instruction Varietates legitimae, 25.I.1994, n.26.
 SCDW, Instruction Varietates legitimae, 25.I.1994, n.66.