Legal Question in Real Estate Law in California

That would depend on why the seller backs out. Real estate purchase contract generally have a lot of opportunities for the buyer or seller to cancel the contract if certain things do or do not happen between when the contract is signed and when it is supposed to close. These are called "contingencies." The contract should have specific terms as to when contingencies are to be removed and under what circumstances. It is not common for the seller to have many contingencies. However, they do have the right to cancel a contract if the buyer fails to remove the buyer's contingencies on time per the contract. There may be other terms in a particular contract that would allow the seller to cancel.

If the seller wrongfully cancels, the buyer has the choice of suing for specific performance, meaning asking for a court order that the seller complete the sale as agreed, or suing for money damages.