If the Pope were Catholic there would be no wrestling going on.
Bingo!
I'm not denying a Pope can go a long ways toward setting the tone. In really flagrant cases he can put depose an errant bishop or put him in charge of some little sinecure in Vatican City (like I think it was JP2 did to the former Archbishop Milingo of Lusaka.)
But ordinarily, the bishop's The Man. The Vatican doesn't have surveillance and enforcement systems all around the globe to get into every disputed case.