In order to prove the non-existence of a tainting rule in the conflict of laws, this article revisits the rules on foreign law illegality, namely the rules in Foster v Driscoll [1929] 1 KB 470 and Ralli Brothers v Compania Naviera Sota y Aznar [1920] 2 KB 287. The results show that they reflect a peculiar and circumscribed rationale of international comity. At the same time, this article considers the implications of recent developments in the law of illegal contracts on the tainting rule. These implications considered together with obligations of international comity show that the tainting rule has either been superseded or is no longer needed to augment or complement the rules on foreign law illegality.