Just a bit of curiosity that hit me recently. There’s certainly a process by which new saints get canonized. Is there one by which previously officially-declared saints are de-canonized? Has this ever occurred?
Sure. A lot have been removed from the list of feast days. That’s certainly a demotion in most respects. Notably where the accounts of the original life of the saint is considered unreliable.
The Master speaks: Who was the worst Catholic saint?
OTOH, to follow up on an implication of the OP, saints canonized under the “modern” (last few centuries) method that involves a waiting period, background checks, trial-grade evidence of extraordinary virtue or martyrdom, a minimum of two miracles, etc. would be darn hard to “decanonize”; I know of none to whom it has happened. The doctrine is that the Holy Spirit would enlighten SOMEONE at the Vatican that something did not add up BEFORE things got as far as canonization. (I say, don’t hold your breath.)
The most common “demotion” is to strike their celebration from the liturgical calendar, letting individual devotees continue to venerate on an unsupported-by-officialdom basis if they so wish. This is what happened in the '60s to “folk saints” such as Christopher and Ursula. Their striking was more of a correction of a wrong entry in the calendar than a demotion for a cause. For instance, there WAS a martyr named Christopher in Roman times, and virtually all martyrs of Rome whose names were recorded were considered “Saints”. Only, we know diddley about his REAL deeds, so we can’t really “celebrate” them, so off the calendar he goes, though he is still a “saint”.
Post Vatican II, a number of saints were “decommissioned”, so to speak. These were mostly saints who were discovered to have been fictional. St. Christopher is the most notable victim of this purge.
Interestingly enough, even though old St. Chris is not an official saint, it’s still pretty easy to get a St. Christopher medal. And I defy you to find a Catholic of a certain age (50+) who still doesn’t pray to St. Christopher before travelling.
That’s quite interesting, and amusing, given that allegedly the same St. Christopher is also still honored in the East, but his life story is far more prosaic. He was a soldier who converted to Christianity and was given the nickname “Christopher” upon his baptism. Essentially, a fairly straightforward martyr-saint.
The whole “carrying people across a river” thing seems to have been a purely western invention. There is more on St. Christopher at http://www.ucc.ie/milmart/chrsorig.html
A summary (quoted from the article):
St. Christopher was a member of the north African tribe of the Marmaritae. He was captured by Roman forces during the emperor Diocletian’s campaign against the Marmaritae in late 301/early 302 and was transported for service in a Roman garrison in or near Antioch in Syria. He was baptised by the refugee bishop Peter of Alexandria and was martyred on 9 July 308. Bishop Peter arranged for the transport of his remains back to Marmarica in 311. He is really identifiable with the Egyptian martyr known as St. Menas. In so far as the author of the lost, original acts of St. Christopher seems both to have been based at Antioch and to have wanted to encourage missionary activity, he is probably identifiable if not as bishop Theophilus the Indian himself, present at Antioch c.351-54, then as one of his circle.
The story about Christopher being a river man who literally “carried Christ” almost certainly got its start from Christopher’s name, which means “Christ Bearer”. I’m sure this was meant in a metaphorical sense intially – “Christopher” was one who “carried Christ in his heart” = “was a Christian”, and the story evolved to fit that metaphorical name to a more literal situation. I’ll bet it got help from unrelated ancient artwork (Orion, for instance, was said to have carried one of Hephaestus’ dwarf assistants to guide him after he was blinded), but I can’t point to any concrete examples.