Apparently he would not need a work permit to work as a priest, see
http://www.cic.gc.ca/english/work/apply-who-nopermit.asp#clergyIf he finds a church that wants to employ him, I suppose they could try seeing if they can get an AEO for him so he can apply under the skilled worker program, that is if he has enough points. His NOC might be either 4154 or 4217. It is also possible that his church can sponsor him for PR under the PNP program of the province where they are located.