seller wants out

I had my offer accepted by the seller in the state of california. the agreement was signed on friday afternoon, however because of the holiday weekend escrow will not officially open until tuesday morning. the seller wants out and has told me he is pulling it off of the market to move into the property himself. is this legal? is the signed purchase agreement legally binding or does it not count until escrow is opened?

[HomeGuru]

I responded on the real estate law board.