What credentials would such a scholar have?
A recommendation from their local bishop?
Academic or journalistic credentials — the kind you get from being a scholar at a real institution of higher learning, or a journalist affiliated with any organization anyone’s ever heard of. You don’t need a letter from your bishop any more than you’d need it at the Library of Congress. Do I need to add that you don’t need to be Catholic, Christian, or anything at all? It’s a scholarly institution, friend. Try to understand what that means.
I know know you want to make Secret Archives out to be a private club where inside-connected Catholics get to snoop through the juicy files — for a friendly contribution, of course. You need to get over this ignorant bigotry.