Is it legal for a company founder to add to the bylaws that nobody has the power to fire him as ceo (law in Colorado, The United States of America)
Sure. If he is the founder, that's up to him. The question is whether I would want to invest in a company if the CEO cannot possibly be removed. So for the founder, the problem is that he won't find investors if he needs them. And obviously without investors, the question of anyone firing him is moot.