Legal Question in Real Estate Law in California

What does it say in the contract? Often there is a clause that says, the seller and his heirs, successors, and assigns. Even if there isn't, a creative lawyer can sometimes find a way to achieve your objective. The answer may depend on the subject matter of the contract -- are we talking about goods? Real estate? Securities?

"Fully executed" is a very tricky term in the situation you describe. The question cannot be answered reliably without clarifying what you mean.

I assume real property is involved (due to the topic heading chosen). If the contract of sale were signed by the parties and contained no conditions yet to be performed by the buyer that would have been a defense by the seller to a suit to compel specific performance, the sale will be regarded as a "done deal" by a court of equity. See In re Dwyer's Estate (1911) 159 Cal. 664.