I was asked about the question of the Washing of the Feet and the Pope's decision to wash the feet of 2 young women on Holy Thursday. There seems to be some great confusion on this, which to my lawyer's mind seems to be based in some misunderstandings about law generally and liturgical law specifically.
Before I begin, just a few caveats. First, I do not believe there is some unchanging theological necessity that limits the washing of feet to 12 men. In other words, I do not have any theological problem to the washing of women's feet on Holy Thursday. As for the symbolism of the action, I tend to think that it is best expressed when the Diocesan Bishop washes the feet of 12 of his priests, but that's just my personal view. However, as I will explain below, I do believe that limiting the washing of feet to men is the current law, and that generally we should have a spirit of obedience to the law, especially in regards the liturgy. Nonetheless, proper authority certainly has the right to change this, but should it be changed it ought to be done in a way proper to the promulgation of law.
First, some background on the liturgical instructions. As most Catholics know, on Holy Thursday priests are permitted (but not required) to include in the Mass of the Lord's Supper the liturgical action known as the Mandatum. This is the washing of the feet in in imitation of Christ's own example, as recounted in the thirteenth chapter of John's Gospel. There Christ tells his Apostles:
You call me Teacher and Lord; and you are right, for so I am. If I then, your Lord and Teacher, have washed your feet, you also ought to wash one another's feet. For I have given you an example, that you also should do as I have done to you.
In the current liturgical books, the Church permits the washing of the feet of twelve men. In the Latin this is very clear, the text uses the word "vir"--meaning men specifically--and not "homo", meaning man generally (i.e., human beings). There is no ambiguity in the liturgical rubric, if the Mandatum is done in the liturgy it is to be done with 12 men.
Keep in mind, however, that this liturgical action is not a Sacrament, nor even a sacramental. That is, it is not the vehicle for grace the way baptism is. When water is poured over the head of a child and the words of baptism said, it effects a change in the child more than his just getting wet. The symbolism of the pouring of water and saying of words is, in effect, the vehicle for God's salvific grace. In this, God mandates not only the grace that is given, but the means through which it comes. For this reason, the Church recognizes that she cannot change the symbol (the pouring water and the words) any more than she can change the grace that flows from it. This is decidedly not the case with the washing of feet. This action is just symbolic, it effects no grace by the working of the action itself, as sacraments do. It only effects a change in that the viewer is stirred to reflect on the action of Christ in seeing it symbolically reenacted in the context of the Liturgy. Thus, the Church is far freer in adapting the symbol to suit changes in time, place, and custom.
In regards to the changeable elements of the liturgy, who has the authority over it? The Second Vatican Council made that abundantly clear in the document Sacrosanctum Concilium, the first Constitution issued by the Council Fathers:
Regulation of the sacred liturgy depends solely on the authority of the Church, that is, on the Apostolic See
Sacrosanctum Concilium 22
That is, the Pope--and the Pope alone--has authority over the sacred liturgy. He normally does that by promulgating the liturgical books.
Is the Pope bound to the authority of the liturgical books? Yes, but remember that he also has the power of dispensation. There are things in the liturgy which are unchangeable--the use of bread and wine, for example--which not even the Pope can derogate from. But for the others--"merely ecclesiastical laws"--the Pope may dispense anyone from them. So, for example, before the Second Vatican Council, to say Mass a priest had to have use of his thumb and index finger to hold the host. The Jesuit Priest--now saint--Isaac Jogues had his fingers removed by the Mohawk Indians then living in Canada, whom he was trying to evangelize. The Pope at the time dispensed him from that liturgical law so that he might continue to say Mass.
The Code of Canon law allows a legitimate authority to dispense from any "merely ecclesiatical law":
Can. 85 A dispensation, that is, the relaxation of a merely ecclesiastical law in a particular case, can be granted, within the limits of their competence, by those who have executive power, and by those who either explicitly or implicitly have the power of dispensing, whether by virtue of the law itself or by lawful delegation.
As a general rule, in the law one who has the power to dispense others has the power to dispense himself, unless explicitly prohibited from doing so. Here, the Pope clearly has the power to dispense from the rule that the washing of the feet be limited to men. In fact, he is the only authority with the power to do so, as the law explicitly reserves the regulation of the Sacred Liturgy to him. Since he has the power to dispense others, he can dispense itself.
Therefore, those who say the Pope somehow acted illicitly by washing the feet of women on Holy Thursday are simply wrong. He has the legal authority to do so, and such an action is completely legitimate.
Now, what about everyone else? A well known Catholic writer issued on Twitter this comment: "The question of whether a priest can wash women's feet on Holy Thursday now seems answered. Pope Francis will do this today in a prison." To the extent that this was an assertion that any priest may now ignore the rubric limiting the washing of feet to men, this is simply wrong and misunderstands the nature of law.
The whole point of "dispensation" is that it derogates from the law in a particular instance. Law, on the other hand, is something of general applicability. Part of the very definition of law is that it must be promulgated by one in authority if it has general effect. To state otherwise would be to say that every dispensation actually changed the law for everyone. That would be chaos. The orderly functioning of any society requires a consistent and coherent set of laws, and a clear delineation of what binds and what does not.
To conclude, Pope Francis was certainly not acting "illegally" by washing the feet of two women on Holy Thursday night in the juvenile prison in Rome. At the same time, the Pope did not change the rubric for anyone else, only for himself on that one Holy Thursday.
If pastors--or Bishops--earnestly believe that there is great spiritual advantage to be had by changing the rule, their course is clear. We are a hierarchical Church that, especially with regards to the liturgy, looks to those who have been given the special charge of preserving that liturgy. Any priest, any Bishop, and even an entire Conference of Bishops, needs simply to petition the Apostolic See for a dispensation of the rule, or request its amendment. Until then, the law should be followed.