Amy, at The Fifty Minute Hour, asks why thugs like Idi Amin live out a cush life instead of spending it spread out on a hill of fire ants(my words, not hers):

The current theory among many Ugandans is that there’s a Muslim conspiracy to protect dictators afoot:

“Why no extradition and trial? One Ugandan theory argues that the Saudis simply will not let an African Muslim potentate be toppled, tried and convicted by a predominantly Christian African state. That’s an argument loaded with religious and ethnic explosives, too hot and politically incorrect to touch. However, East Africans I know believe it. Post 9-11, it may not seem so outlandish.”

The argument, true or not, raises an obvious question. Why is the international community willing to bow to the will of Saudi Arabia on the issue of human rights in Africa? The Saudis certainly have an opinion as to what should happen to dictators like Amin, but why does their view prevail?

Read her interesting answers here. Andrew Case, in the comment thread, suggests what I think may often be the answer: the unbothered retirement was the payoff for the thug(s) to step down.