So much for Matthew’s contention that nobody here is justifying the recreational use of MJ.

I have nothing more to add.

Good. You should extend your Cathinfo fast through Pentecost. And while you’re waiting, buy this one (it’s very cheap) and read the section on intemperance:

https://www.lulu.com/en/us/shop/edward-farrell-and-charles-callan-and-john-mchugh/moral-theology/paperback/product-5j9rnz.html?page=1&pageSize=4

Jone, Prummer, and McHugh’s Moral Theology all say the same thing. You’re beaten. 

A social stigma (i.e. most people don't consider it "normal") doesn't mean it's a moral scandal.  Most people consider buying whiskey/vodka at the liquor store to be "normal"...but they would not ever consider drinking safely-produced moonshine (because it's "weird" and "not safe").  There is a social stigma attached to moonshine (same as MJ) due to potential illegality but this is not the same as a true, moral scandal.

You could also argue that seeing a priest/nun wearing a sports team hat or wearing Nike tennis shoes would be a "scandal" (there are many degrees of scandal and also some people misuse the word instead of "shock") but it wouldn't necessarily be a sin.  Much like post-V2 priests starting wanting to be called "Fr Jim" instead of using their last names...is that a sin?  I can't say for sure, but it surely is a social norm they are deteriorating.  Priests/nuns are a special class of person so using them in an argument is dumb.

Good. You should extend your Cathinfo fast through Pentecost. And while you’re waiting, buy this one (it’s very cheap) and read the section on intemperance:

https://www.lulu.com/en/us/shop/edward-farrell-and-charles-callan-and-john-mchugh/moral-theology/paperback/product-5j9rnz.html?page=1&pageSize=4

Jone, Prummer, and McHugh’s Moral Theology all say the same thing. You’re beaten.

Can you quote the parts where they specifically address the morality of recreational use of Marijuana?

”No Sean, they just lay out the principles which pertain to intoxication.”

OK, then (leaving aside the insufficiency and error of those who have limited their moral conclusions by only addressing the issue of intoxication), here’s an article for you addressing the morality of recreational MJ use according to the principles of St. Thomas Aquinas (discussing both the matter of intoxication, as well as additional morally aggravating circuмstances):

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5102207/

Introductory excerpt:

Abstract

Several empirical studies suggest that recreational marijuana is popularly perceived as an essentially harmless rite of passage that ends as young people settle into their careers and their adult intimate relationships. Is this perception accurate? To answer this question, we evaluate the morality of recreational marijuana use from a virtue perspective guided by the theological synthesis of St. Thomas Aquinas. Since the medical data reveals that recreational marijuana use is detrimental to the well-being of the user, we conclude that it is a vicious activity, an instance of the vice of intoxication, and as such would be morally illicit.

Lay summary
In contrast to its medical use, the recreational use of marijuana cannot be justified for at least three reasons. First, as scientists have amply docuмented, it harms the organic functioning of the human body. Second, it impedes our ability to reason and in so doing does harm to us. Finally, it has lasting detrimental effects on the user and his neighbor, even when it occurs in a casual setting. Intoxication is always contrary to the integral good of the person. Thus, the use of marijuana is never warranted even for good, non-medical reasons.

Excerpt from a 2019 SSPX article (Note this article discusses recreational use, not medical use):

Is Using Marijuana a Sin?
The primary effect of the THC is to induce the “high,” and it is practically very rare that one could effectively avoid the stultifying effects of the drug.
For all of the above reasons – that is, impairing of the ability to think and judge properly, damage to the brain, fleeing from reality, unknown physical or psychosomatic effects, difficulty in dosing - moralists conclude that, even though the use of marijuana does not entirely totally suppress the use of reason, it is certainly gravely imprudent to use it.
Thus, the deliberate use of marijuana for recreational purposes is a mortal sin.“


https://florida.sspx.org/en/news-events/news/get-pot-just-say-no-47742

So, a single "primary" false premise is spun hysterically into a plural, "all the above reasons."

And from that false premise—a gratuitous denial of dose titration—the entire pseudo-syllogism falls.

Please add the rejection of pre-Vatican II moral theology to "As We Are."

Lay summary
In contrast to its medical use, the recreational use of marijuana cannot be justified for at least three reasons. First, as scientists have amply docuмented, it harms the organic functioning of the human body. Second, it impedes our ability to reason and in so doing does harm to us. Finally, it has lasting detrimental effects on the user and his neighbor, even when it occurs in a casual setting. Intoxication is always contrary to the integral good of the person. Thus, the use of marijuana is never warranted even for good, non-medical reasons.

Sean, your Summary used the word "intoxication".  That's not what we're discussing...

I would submit that 100% of these people would be scandalized *just as much* or 99% as much by those same priests/nuns lighting up a regular cigarette. And so...

No doubt.  For 20+ years I have been told by ignorant, ill-formed, busybodies throughout Traddieland that I shouldn't smoke -- many times in the parking lot after Mass at this or that chapel.  Usually, they say something like, "You shouldn't smoke; it isn't good for your health."  My response has always been, "You shouldn't tell people (you don't know very well and who are 6'3", 200+) what they should or should not do; it isn't good for your health."  Not surprisingly, that ends the conversation, at least on that one, silly point.

Can you quote the parts where they specifically address the morality of recreational use of Marijuana?

Sure! In my 1961 edition of Jone, section 110, he lays out the principles for intoxication, rules we are probably all familiar with. Subsection c) says the following:

Since morphine, opium, chloroform and similar drugs can also deprive one of the use of his reason temporarily, that which was said of intoxicating drinks holds also for narcotics.

To use narcotics in small quantities and only occasionally, is a venial sin if done without a sufficient reason. Any proportionately good reason justifies their use, e.g., to calm the nerves, dispel insomnia, etc. Such use becomes gravely sinful if it creates an habitual craving for "dope", which is more difficult to overcome than dipsomania and more injurious to health.