A large majority of researchers in my field publish in Elsevier journals. However, a professor who is widely regarded as an authority in my field has, some years ago, signed The Cost of Knowledge pledge to neither publish nor review for Elsevier. I think this is sad, since someone who is highly qualified to review these papers will no longer review them and improve their quality.
This professor has published in other journals, but it does not seem that others are following suit, since these Elsevier journals seem to be highly prized. What can he do to be able to review papers that would have otherwise come to his perusal without having to recant?