Legal Question in Real Estate Law in California

Re: option to buy

An option to buy, when exercised, obligates the owner to sell.

This is an oversimplified answer, but your question also lacks any details. Are we talking about real estate, or stocks and bonds?

An owner who may be obligated to sell upon the exercise or attempted exercise of an option may have rights and defenses, such as the option holder's failure, or inability, to tender the purchase price; prior expiration of the option through time lapse or option holder's breach of a condition precedent, etc.

If the option involves real property or other unique property (e.g., artwork) the owner can sometimes be forced to sell, i.e. money damages alone are not considered an adequate remedy.