You need to talk to an attorney. Having said that, it is my understanding that any contract to purchase real estate must be in writing, so if you are referring to the agreement to sell it back to them, it's not the bank you have to worry about, it's a court of law because the agreement was verbal. There may also be an issue with the bank. Every short sale I have ever worked on required the buyer and seller to sign an affidavit stating this was an arms length transaction, meaning the buyer and seller had no private agreements. So, trying to enforce this agreement to sell the home back to them could also be a problem since it was a private agreement you had on the side. Please consult with an attorney to confirm this is the case. Every State has slightly different laws.