I have chewed over this question and sought advice from people who are usually decisive as well as reliable, and I'm afraid I can't give you an authoritative reply. On the whole the lawyers think that because the law doesn't establish a procedure, there isn't one, so the decision not to be a governor is final, whereas most people working in the service can't see any reason why the law should spell it out when there isn't in their view anything wrong with a change of mind.
I myself am firmly in the latter camp and in practice it is what most people assume to be the case. I don't see why a new head's decision can't be reconsidered in the light of experience, and indeed I think it would be very harsh to disallow it. Many newly appointed heads don't know much about governance, fear the unknown, and are quite likely to make a "safe" choice (recommended by their association in times past) and then regret it.
They may also tend to follow what their predecessor or the head of their former school did until they see the lie of the land, and to hold them to this decision is to perpetuate an old culture.
I confess that I may be influenced in this by very much hoping that in time heads will want to be a part of their governing bodies and believing that progress in this direction is more likely if reconsideration is allowed. I also have noted over the years that legislation is hardly ever explicit on what you can do, and our activity would be very limited if we didn't assume that anything not forbidden was all right.
If local rules provide no guidance, I suggest that a governing body might like to discuss the issue before need arises and establish their own procedures, including the amount of notice of a change of mind and perhaps a limit on the number of changes. I certainly wouldn't approve of "hopping in and out" of governorship according to expediency.
I think it is also helpful if LEAs, governor trainers, governing bodies, gently make the point that being a governor is a legal right which shouldn't be rejected lightly or hastily.
Questions for Joan Sallis should be sent to Agenda, The TES, Admiral House, 66-68 East Smithfield, London E1 9XY. Fax: 0171-782 3200.