Here's some reporting from SI:
... "But leaving the ACC could be costly owing to the league's grant of rights agreement. Any school that leaves before 2036 would have to give its media revenue to the ACC through that year, or else pay a major exit fee rumored to be around $100 million.
But reports also indicate that Notre Dame could avoid some of that bill, which could be lower given that the school's football program wouldn't be part of that deal.
Any fee that ND would have to pay, the school would likely make back in a year or two of being in the Big Ten."
@goldendomer : is that your understanding? If so, I don't think the GOR would hold them back from leaving the ACC.