I happen to run into the Pope, who says: "Hey, you better shape up and obey canon #1753. No carbonated drinks on Friday."
Me: "There isn't any such canon, Your Holiness."
Pope: "Yes there is. This morning, I told a Swiss Guard outside St. Peter's that I made the new law. That was the promulgation."
Pope at Mass: "As of now, I can and will promulgate law in whatever way I see fit."
Me meeting the Pope after Mass: "Ok. I suppose you can do that, canon 331 and all....might be a bit difficult for us to keep up, though, and it doesn't seem practical."
The next month, the Pope tells a Swiss Guard about c. 1753. Later that day, he meets me and we have the above conversation, but concluding with me saying "Oh. If you say so."
The Holy See makes public a document whereby the Pope states that he is amending the Code of Canon Law by adding c. 1753: no carbonated drinks on Friday. The law is in effect immediately. The next week, I run into the Pope with my caffeinated, carbonated, filtered water (they probably actually sell something like that) but have to toss it when he reminds me of the law.
In the first instance, the Pope has no reason to expect that I will take him seriously. To me, it would be more likely that he would only say such things in jest. In the second instance, my obligation to follow the new law is clear. The Pope made it possible for me to have some certainty as to what he was doing and what I was supposed to do, even though it was a surprise to me. In the third instance, nobody has any question about the existence of the law. I just forgot about it.
Let's consider another possibility. Pope Francis, in one of his patented interviews, says: "Carbonated drinks really aren't appropriate on Friday, when we should be performing penance. I've heard that Pope Benedict XVI never drank his Fanta on Friday. Let's all follow his example." Some people might respond by saying that this is now "the law of the land": no one is permitted to drink such things--at least Fanta--on Friday. I would beg to differ since such a comment doesn't mean much from a legal perspective.
These days, one can see an "antinomian" tendency from time to time. There can also be a misunderstanding of how the law works, especially in regard to the role of the Pope. Essentially, some might think the Pope's words are necessarily legislative works: whatever he says about something that has any connection, however remote, to the law is to be taken as a legislative, executive, or judicial declaration. This is not antinomianism but is problematic. I'll call it ignominianism or maybe Yul Brynnerism. No, the Pope is not Rameses II, as portrayed by Yul Brynner.
Both the law itself and the way it comes into being has to be rational and orderly. When there is an official, established method for law to be "promulgated" everyone can expect that all legislators will follow that method. In the absence of order in how a law comes into being, there is necessarily an absence of certainty as to what the law is. While the law exists, we rightly expect even the Pope to abide by it. If he intends to change the law, there is an established, legal and orderly way to go about it. If he doesn't follow that "way" then it is reasonable to conclude that he is not operating in the canonical, legal sphere. His words are to be taken in, for example, a pastoral, exhortative tone, not in a legal one.
Here are a few remarks from St. John Paul II on the role of law in the Church:
2. ... In the Church, then, the purpose of law is the defense and promotion of the “glorious liberty of the children of God” (Rom 8:21); this is the Good News which Christ sends us to bring to the world. To see the law as spiritually liberating runs against the grain of a certain understanding of law in Western culture, which tends to view law as a necessary evil, a kind of control required to guard fragile human rights and restrain wayward human passions, but which would disappear in the best of all possible worlds. This is not the biblical view; nor can it be the Church’s view. ... Ecclesiastical law gives form to the community or social body of the Church, always with a view to that supreme objective which is the salvation of souls (cf. Canons 747, 978, 1752). Since this ultimate end is attained above all through the newness of life in the Spirit, the provisions of the law aim at safeguarding and fostering Christian life by regulating the exercise of faith, the sacraments, charity and ecclesiastical government.
3. The common good which the law protects and promotes is not a mere external order, but the sum of those conditions which make possible the spiritual and internal reality of communion with God and communion between the members of the Church. Consequently, as a basic rule, ecclesiastical laws bind in conscience. In other words, obedience to the law is not a mere external submission to authority but a means of growing in faith, charity and holiness, under the guidance and by the grace of the Holy Spirit. ...
6. Dear Brother Bishops, the purpose of these brief considerations is to encourage you in overseeing the faithful application of canonical legislation: this is essential if the Church is to show herself ever more equal to the task of carrying out her salvific mission.... A deeper appreciation of the importance of canon law in the life of the Church and the implementation of measures to guarantee a more effective and conscientious administration of justice must be a central concern of your Episcopal ministry. Fidelity to ecclesiastical law should be a vital part of the renewal of your particular Churches.