I do not think that there is an actual statutory rule about this matter,certainly not one that I can easily find. I think therefore that the governing factor will be what is contained in the articles of association about this matter provided ,of course, that the articles themselves are not in breach of the law and as a result can not be upheld.In the model articles of association for public companies the company is allowed to exercise a lien over unpaid partly paid shares and sell them on to someone else after following a proscribed course of action.Further details of this process can be found in the Model Articles For Public Companies Schedule 3, Sections 52 and 53.