In ruling for the former mayor, the justices drew a distinction between bribery, which requires proof of an illegal deal, and a gratuity that can be a gift or a reward for a past favor. They said the officials may be charged and prosecuted for bribery, but not for simply taking money for past favors if there was no proof of an illicit deal.
I was just going to post that, it seems more like the onion:
Supreme Court wipes out anti-corruption law that bars officials from taking gifts for past favors