Just one of those things that popped into my head. I know Popes frequently celebrate Mass outside, Paul VI celebrated Mass at Yankee Stadium, I think JPII celebrated at Giant stadium, etc. Basically every time a pope has come to the US he’s celebrated Mass in a sports stadium and probably does it in most countries he visits.
Now I was always told that Mass had to be celebrated inside a church and I would think that at least on consecrated ground, but obviously Yankee stadium and Giant stadium are none of the above. So what are the requirements that have to be met to celebrate a Mass outside? Can a priest do it? A Bishop? Or is it only the Pope?