In answer to heric's question: Yes, I think they can do this without GWB's permission, at least in America, because GWB is a "public figure." Legally, it's no different from drawing a caricature of him in an editorial cartoon, or putting his picture on the cover of a book about him (e.g. Molly Ivins' Shrub).

Click here for an article about the Princess of Wales Memorial Fund vs. The Franklin Mint.