he shouldn't be allowed to sell his story to the papers.
How do you propose that he is prevented?
Abandon the now entrenched free enterprise principles of the market economy that everyone now holds dear?
Censor free speech?
Imprison him?
Or, somewhat more practically, you could stop giving money to the publishers of such kill-and-tell stories. Moreover, you could stop buying anything that makes overblown celebrities out of TV presenters, which is the element that features hugely in the death of Jill Dando in the first place.