It is an axiom of the conflict of laws that one state will not enforce the revenue, penal, or ‘other public’ laws of another. This thesis shall criticise this position, arguing that these exclusionary principles should be replaced with a general principle of enforceability, subject to the control of public policy. It shall begin by sketching the general landscape of the exclusion of foreign law in Anglo-Scots international private law. Thereafter, a detailed account shall be given – for each of the revenue, penal, and ‘other public’ law rules – of the historical development of those exclusions, and their present scope of operation. This exposition provides a foundation for a critical examination of those rules.