Bottom line - a contract is a contract is a contract.
Hartlepool have every legal right to expect Joel to honour his contract as we expect our players to honour theirs.
We can negotiate a transfer fee with Hartlepool or move on.
Unless it is an illegal contract. Or void. Or there is an implied term. Or it's unconscionable to enforce it. etc etc. Contract law has plenty of loopholes and without the facts its pretty hard to make a comment either way. Sounds like it could be a situation where the only winners are the lawyers.