"So, the question is: is the pope a head of state, and therefore possess diplomatic immunity?
The answer is: Yes. Even though the Vatican does not conduct its own diplomatic relations, it does have sovereign status within its own borders. Having diplomatic relations has never been a criteria for statehood.
People don't have to like it, but they do need to recognize that he's untouchable unless any crime he is suspected to have committed falls within the jursidiction of the International Criminal Court. I'm no expert in international law, but I sincerely doubt it."