There is no available remedy under international law. The Americans have had some success with offering multi-million dollar rewards – they found Uday Saddam Hussein in that way and dealt him justice the same day. Perhaps a humanitarian minded African billionaire might be that way inclined, failing that, what is Ross Perot doing nowadays?
That “what if” discussion as to whether assassinating Hitler in 1940 would have saved the jews seems to be relevant to contemporary Zimbabwe. The country has become a giant death camp, a hungry bedraggled populace and thousands dying in the streets from cholera.