Is it against the rubrics or other liturgical laws, for the priest to recite the words and formula of absolution in the vernacular, rather than in Latin? 

I have had this happen on the odd occasion, most notably at Christ the King Abbey in Alabama while Father Abbot Leonard Giardina was still living (it was another priest besides Father Abbot Leonard).

And why would a priest choose to do this?  Is it an option that exists?  There can't be any question as to validity.

I’d be shocked if there weren’t approved English translations of the Rituale out there and I bet the ordinaries were able to give permission for these to be used.  If a priest said, “I absolve you of/from your sins” ... or “I baptize you ...”. I’m sure those would be perfectly valid.

Concur with Lad.

I'm referring to traditional rites only.  I do not challenge the authority of the Pope or the bishops (assuming they are indeed Catholic, and thus are able to BE the Pope or a bishop) to confer permission to administer sacraments in the vernacular.  My question merely was whether vernacular translations of the various rites of the sacraments (absolution, baptism, extreme unction, etc.) exist at any official level in the pre-1969 rites, and whether they may be used licitly.  In the case of vernacular absolution, I first encountered this at Christ the King Abbey in Alabama when Father Abbot Leonard Giardina was there, and I just assumed that, for some pastoral reason, he was within his authority as abbot (assuming that he actually had this authority, it could be argued both ways) to implement such a thing.

So far as I am aware, there is no official translation of the Tridentine Latin Mass into any vernacular, aside from isolated situations in ƈhıną and Croatia (WRT the latter, it was not vernacular Croatian, but some kind of Old Church Slavonic).

The only one I was aware of was Pius XII’s introduction of the vernacular into his new Holy Week rites.

Apparently, he also allowed it in ƈhıną and Indonesia generally (excepting the Canon; see link below).

Also:

“Though insisting on the primacy of Latin in the liturgy of the Western Church (cf. Mediator Dei, par. 60), Pius approves the use of the vernacular in the Ritual for sacraments and other rites outside the Mass. All such permissions, however, were to be granted by the Holy See, and Pius XII strongly condemned the efforts of individual priests and communities to introduce the vernacular on their own authority. He allowed the use of the vernacular in other rites and sacraments outside the Mass,^[6] in the service for Baptism and Extreme Unction.^[7]”

https://en.m.wikipedia.org/wiki/Liturgical_reforms_of_Pope_Pius_XII

Got it.  It seems that pre-1962 vernacularization was more widespread that I had thought.

I know this has been said by many other people through the years, but if it were a question of people genuinely responding better to the Mass ("responding" here meaning both internally, i.e., mentally, and in external responses), and nothing more than that, then I could live with dignified, literary vernacular translations of the Tridentine Rite, approved by the Holy See.  I don't need it myself, but clearly some people saw the need even then.

Of course, there was much more to it than that, and it wasn't all about just language.  But everyone here knows that.

Well, they “saw the need,” but for all the wrong reasons (ecuмenism).

The history of the liturgical movement (since the 1910’s) is the history of the rapprochement with Prots.

Well, they “saw the need,” but for all the wrong reasons (ecuмenism).

The history of the liturgical movement (since the 1910’s) is the history of the rapprochement with Prots.

You raise an interesting point, from which I could segue in several different directions.

I'm willing to go out on kind of a limb here (or maybe it's not such a limb after all) and say that the whole movement for vernacularization was driven by Protestantism.  Beginning in the early 20th century, Catholics were becoming more and more aware of what Protestantism was all about, they interacted with Protestants, saw "they're not so bad after all" (and they're not, they're good people with a bad, because incomplete and heretical, religion), and in the most natural human impulse there is, deep down, wanted to be like them.  After WWII (and I speak mostly from an American perspective), people mixed more, interacted more with each other, lived in the same neighborhoods and, yes, married each other.  First there was radio, then there were movies and television, then more people started going to college, and things just kind of took on a life of their own.  Having large families became more burdensome (financially most of all) about the same time that birth control, in various forms, became more available.  In a nutshell, Catholics wanted "what all the other kids on the block have", and through being coached from above, from Bugnini on down, they came to the notion that "our liturgy needs to be more relevant" (i.e., to modern life, things can't be "relevant" on their own, they have to be "relevant" in relation to something else).  And, of course, there was the obedience thing.  If there is one hallmark of the classical Catholic, it is obedience.  Whatever Father says is the end of the line.  The Pill came along, there was at least a probable (if less probable) opinion that it might be okay because it might be in some sense "natural", Paul VI had to tell the world, sorry, no, it's not, people didn't want to obey, and there was no shortage of priests to tell them that it's okay, my dear friends, you don't have to go along with this one thing.  Humanae vitae in 1968, the New Mass in 1969, and as Audrey Hepburn cried out when the drunk woman passed out at the cocktail party in Breakfast at Tiffany's... TIMBERRRRR....

So much more where that came from, but you get the idea.

What happened to the Catholic Church in 1968 and 1969 can be seen here at around 4:05 ---