In legal docuмents, words like "perpetual" mean the law has no defined end date. It continues to be law unless it is abrogated. It does not mean the law can never be abrogated. For example, consider how no one would argue that "perpetual peace treaties" mean any future wars are illegal. https://blog.oup.com/2017/10/perpetual-peace/

Obviously.  So the question becomes:  does the addition of St Joseph change the rite?  Probably not.  (but I don't believe this change was done legally, so the question is moot).

As I mentioned, since the Communicantes already concludes the section with "and of all the saints," there is actually zero change in the meaning, since St. Joseph is already included in "all the saints" and calling out his name explicitly changes absolutely nothing.  So there's no "probably" not about it.  It most certainly does not change the meaning of the sentence in any way whatsoever.

That's like saying, in Latin, "ego te absolvo ..." is different from "te absolvo ..."  Both are identical, with the first merely adding a bit of emphasis.

In addition, the part of the Canon where the departed faithful are commemorated is already "changeable", as the priest is permitted to insert names of his own choosing.  So I see very little difference here.

Dear ElwinRansom1970,
Thank you very much for your explanation.  Please explain the relationship between "liturgy" and "discipline".  Could you refer us to a relevant docuмent or book?  Thank you for your help!

Here is a place to begin:

Fortescue, Adrian. The Mass: A Study of the Roman Liturgy. (London, New York: Longmans, Green & Co., 2912)

Some trads love Fortescue because he is not Josef Jungmann and Michael Davies promoted Fortescue. However, Fortescue was an academic which means that what he actually has written can seem modernistic to trad ears. He really isn't if one reads carefully.

But never be a person of one book! Look at Jungmann. Look at Gueranger! Look at Schneeman!

Or even learn like a scholar:  Go to Le Dictionnaire de Théologie Catholique and the New Catholic Encyclopedia and compile bibliographies from the sources used to create entries in these reference books. Go read those books and note the sources you find there for an ever-growing bibliography. Keep going until you start cycling back to already examined sources.

I have seen the readings of the Mass, liturgy, and I don't like them.  The thou, thee, thy went to you, you, you and your.  It decreases God to you.  I am not happy with it. St. Joseph is just a way a putting a toe in the door for more changes.  I would have been happy to see at least the addition Holy ghost the Paraclete to the Divine Graces, and adding Blessed be His Most Precious Blood. They added St. Joseph there, but not the Holy Ghost?

Oh, they did! Once a NO enthusiast tried to convince me that the Eucharistic Prayers II-IV were improvements on the Roman Canon precisely because they mentioned the Holy Ghost.

In reply nr.2 Stubborn provided the quote from "Quo Primum" - nothing must be added, nothing omitted, nor anything whatsoever be changed.

In reply nr.27 OABrownson1876 offered when the Canon begins, but not where it ends.

In reply nr.29 Angelus offered the Chapter IV from the XXII Session of the Council of Trent and its Canon VI which is the conclusion that the Canon of the Mass does not contain error and cannot be abrogated.
Also, "Canon" means "measuring line" or "the rule".

In reply nr.32 DecemRationis offered Bull "Exultate Deo" of Pope Eugene IV confirming the teaching of the Council of Florence. The form of the Sacrament of the Eucharist are the words of the Saviour with which He effected this Sacrament, and the quote from Matthew 24.

In reply nr.34 DecemRationis offered "Now, I say those Divine Elements refer to those pertaining to the Sacrament of the Eucharist of which the Mass is the vehicle". The Mass is the vehicle for the Sacrament of the Eucharist.

In reply nr.44 Angelus offered the quote from the Catholic Encyclopedia : "The Council of Trent (1545-63) restrained this tendency and ordered that ' the holy Canon composed many centuries ago' should be kept pure and unchanged."

In reply nr.54 DecemRationis offered the Bull "Apostolicae Curae". The Church is forbidden to change or even touch the matter or form of any Sacrament. She may indeed change or abolish or introduce something in non essential rites or "ceremonial" parts to be used in the administration of the Sacraments, such as processions, prayers or hymns, before or after the actual words of the form and recited nr.45 of the Bull.

In reply nr.57 Stubborn used the word "codified", but did not define it.

In reply nr.65 DecemRationis offered "The substance of a Sacrament consists of those elements which are absolutely necessary in order to have the Sacrament; viz, the matter and form. ... The form is the sequence of specific, determinate words pronounced by the minister of the Sacrament."

In reply nr.68 DecemRationis brings up "Quod a Nobis", the Bull concerning the Breviary.

Next follow several posts about binding authority of the Popes. No quotes, no explanation of what is the scope of binding in law, in discipline, in liturgy.

In reply nr.134 ElwinRansom1970 offered: The Canon is the anaphora, or Eucharistic prayer, for the Roman Rite.
The Canon begins properly with Te Igitur and concludes with the Per Ipsum. The Canon is unchanged from the VIIth century until 1962 addition of the name of St. Joseph. No explanation of the relationship between liturgy and the discipline.

At this time only Angelus has given direct quotes concerning the immutability of the Canon in replies ns. 29 and 44. There are no quotes  supporting the possibility of any changes to the Canon. 

To return on the original path, I provide the quote from the study of the rubrics of the Roman Missal: "The sacred liturgy consists in: 
(i) The sacrificial liturgy (the celebration of the Mass),
(ii) The sacramental liturgy (the making and administration of the sacraments and sacramentals),
(iii) The epenetic liturgy (the singing and recitation of the Canonical Hours)
Of these three parts the most important, and the centre of the entire liturgy, is the Sacrifice. This is prepared for, and duly acknowledged by, the Divine Office." (p. 5 The Celebration of Mass, Rev. J.B. O'Connell, The Bruce Publishing Co. Milwaukee 1964)

The venture into "Quod Nobis" and the language used as compared to "Quo Primum" is important, but one must understand the difference between the epenetic and sacrificial liturgy. I dare say, the sacrificial liturgy, has the sacramental part in it, while the epenetic does not.