First of all, the Catechism of the Catholic Church states:
“2291 The use of drugs inflicts very grave damage on human health and life. Their use, except on strictly therapeutic grounds, is a grave offense. Clandestine production of and trafficking in drugs are scandalous practices. They constitute direct co-operation in evil, since they encourage people to practices gravely contrary to the moral law.” (
vatican.va/archive/ccc_css/archive/catechism/p3s2c2a5.htm)
Here we see drug used condemned as a “grave offense”, which means it is a mortal sin if done with sufficient knowledge and consent to constitute a deliberate choice to commit the sin. We do have to look closer though. Exactly what kinds of drugs are meant, for example?
Common sense says this is not referring to drugs such as, say, caffeine. From some commentary that I’ve read on the passage, the official Latin text here reads what would literally be translated as “stupefying drugs.” This official Latin text was itself based on an original French text, though it is the Latin that is authoritative. This original French text, like the English translation, simply says “drugs.” It would seem as though the original French and current English are using the word in the modern colloquial sense, while the more permanent Latin version is more specific as it’s the version that translations a thousand years from now would be based on, when the modern colloquial sense of the word “drugs” may have disappeared. Anyway, marijuana would almost certainly be considered a “drug” in this modern colloquial sense.
On the other hand, is marijuana as dangerous for one’s healthy as alcohol, the moderate use of which the Catholic Church has always accepted? It seems not. And the focus of the Catechism passage is clearly health consequences of drug use, since the passage is a part of the section on the commandment “thou shalt not kill” and so is focused on dangers to human life. Therefore one might come to the conclusion that marijuana should be exempted from the Catechism’s general condemnation of drug use.
Still, there are other ways something might be sinful. One would be if it violated a legitimate civil law, for example. In the United States it does so, even in places where actual penalties have been reduced or eliminated. There is an exception for unjust laws, which are not true laws at all in the moral sense, but one would have to identify an actual injustice which the law brings about, and that does not seem to be the case here.
Finally, the use of marijuana could be interpreted as a form of the sin of gluttony, because it seeks pleasure outside of any rational, morally licit context such as eating and drinking (well, most of the time at least, and even when it is added into food this is not done for any nutritional reason). However, this rigorous interpretation of the sin of gluttony, which in its strictest interpretation would also forbid any kind of condiments, has never been a mainstream way of thinking outside the monasteries and seems to be met with skepticism by most modern Catholics who encounter it.
In all, my opinion is that for regions in which it is legalized the case against marijuana seems a little weak, though my own moral instincts are still strongly against it. In most places though the drug remains illegal, and that fact would seem to close the door on the possibility of morally licit use (except perhaps on strictly therapeutic grounds in places this is legal).
