Here in Germany nobody would move based on an offer, only based on a signed employment contract. Of course you can terminate the contract, but there commonly is a clause that you can't terminate the contract before it starts (to protect both parties from the other party backing out). And even if that clause doesn't exist, by law there is at a minimum a two week notice period, so this example of a company walking back on it a week before isn't possible. And while relocation reimbursements typically would contain a clause that effectively vests it over X years (meaning you have to pay part of it back if you quit) this clause legally can't apply in a case like this where there's no fault of the employee (he wasn't even there to potentially do something wrong).

Despite these basic protections, we still manage to hire people around here.