“Does it even make sense to consider a religion also a diplomatic state?”
The Vatican is a state by its own proclamation, not by ours, and they certainly have that right. Any nation calling itself an “islamic republic” is essentially doing the same thing.
But it doesn’t make sense over here.
It’s not like bishops and archbishops and cardinals can break the law here and claim diplomatic immunity. cardinals and archbishops are regarded as ambassador-type diplomats, but they can be arrested.
SO they’re a nation but their diplomats (high officials) aren’t afforded diplomatic immunity. are they diplomats or aren’t they?
muslim clerics here don’t have diplomatic immunity either.
Actually, the Vatican is not sovereign by its own proclamation: in 756 Pepin the Short, who was sovereign over (among other things) the portion of the Italian peninsula that included Rome granted Pope Stephen I sovereignty over Rome and its environs, a grant that was confirmed by Pepin’s son Charlegmagne in 774. The size of the Papal States have ebbed and flowed since then, but the sovereignty is by grant, not by self-proclamation. Very few states have such ancient roots.