What are legitimate reasons for a Catholic priest to take a sabbatical? Some of the priests I know were recently given a sabbatical year (in both cases it wasn't for the sake of study - the priests ended their parish assignments lasting for many years and had time to think over whether to take another parish, enter a monastery or leave priesthood completely). When looking for details how sabbatical works for Catholic priests, I found a document concerning archdiocese of Seattle - this seems to expect the priest on a sabbatical to study some special program.

So here are my questions:

1) What does Canon law say about sabbaticals (link to particular canons + brief summary should be OK)?

2) What is up to the Ordinary? How usual is the linked policy, and how different is practice in other dioceses? What reasons for sabbatical are accepted (provided that other requirements have been met) in most dioceses, what in some and what almost never?

I'm interrested especially in situations like that of the two priests I mentioned, but any other information about priests' sabbaticals is welcome.
1) Nothing. Canon law is silent on sabbaticals. It's a completely discretionary thing.

2) Priests' sabbaticals can be many things. Some go on to write a book. Others indeed do study -- one of my university friends was a Catholic priest from Australia who came to Oxford, on a sabbatical, to study for a doctorate. During a sabbatical, at least for reasons of study, their faculties remain intact, but they should in general restrict themselves to co-celebration of Mass. Then there are sabbaticals for health reasons -- usually, policies there tend to be subject to diocesan policies on safeguarding the health (mental, physical and spiritual) of priests. Finally, there are sabbaticals for 'other reasons', these tend to be either giving priests some time to think things through (especially if they somehow were affected by a serious incident or experience a crisis in faith, which happens even to priests!) or as a 'lite' version of suspension. The ordinary has pretty unfettered discretion in this area, subject to, of course, not really having much of a choice where a priest is subject to incapacitating illness. Lately, given the recognition that priests are under an enormous amount of stress and need some care themselves, policies are arguably such that they're more likely to give priests some time if they so need. Sorry that's a bit of a disappointing answer, but sadly that's the best one can do when something's up to the about 400 or so dioceses that make up the Church!