I suppose that on the one hand you’d like the Church’s leaders to be more responsive to the need for justice in apprehending fugitives. On the other hand, the prosecutor’s letter is a bit ham-handed and may perhaps have been more for show than to bring about the desired effect.
For one thing, I don’t think you have county prosecutors contacting ministers of state of foreign nations (which the Holy See is) on their hand. It’s likely that the letter was returned because it did not follow proper diplomatic channels such as going through the State Department or the apostolic nuncio first.
For another thing, demanding the Secretary of State issue direct orders to priests in Ireland and Mexico is a little unrealistic. It would probably be more profitable to work with the local bishop in Phoenix (currently apostolic administrator Archbishop Michael Sheehan) and through him with the local bishops where those priests are. Even so, there’s nothing compelling those priests to obey. Don’t we have extradition treaties with Mexico and Ireland? Why not get the assistance of local law enforcement to arrest them and return them?
A lot of questions, but not a lot of answers. But it is good publicity for the Phoenix DA.