In response to a recent post of mine on the titular question, the invaluable Keith Paul Bishop explains:
As a question of agency law, I agree that a board could delegate to the CEO decisions as to when, whether and on what terms the corporation could be sold. However, Section 300 of the California Corporations Code provides that the business and affairs of the corporation shall be managed and all corporate powers shall be exercised under the "ultimate direction of the board". Thus, it is possible that a court would conclude that a grant of unfettered discretion would constitute an abdication of the "ultimate direction of the board".
I agree. He goes on to review additional reasons that would be a very dubious idea as a matter of law.