Three Theoretical Frameworks
In order to understand the role of international law before a domestic tribunal the conceptual framework for the relationship of the two fields of law must be appreciated. In this regard, international legal writers usually mention at least two strongly opposing schools of thought, namely, the monist and dualist schools.[486]
Expressed in its simplest form, the monist view of the relationship of international law and municipal law is a holistic, unified one: international law and municipal law are seen as part of a single legal order.
Most commonly, monist theories view international law as sitting at the apex of this order, being a superior set of legal norms from which national legal orders derive their validity. From this viewpoint, international law takes precedence over domestic law. The dualist view, in contrast, suggests that international law and municipal law are two competing legal orders with, most commonly, the municipal order taking priority. In some formulations, dualist theorists foresee the possibility of direct conflict between the two legal orders, envisaging, for example, cases in which a tribunal is forced to choose between applying a rule of international law or a rule of domestic law.A third position is suggested by Sir Gerald Fitzmaurice, who views international law and municipal law as distinct legal orders, or different
fields of law, which can never conflict.[487] For him, each body of law sets out rules applicable only in its own legal order — in the same manner that, for example, the laws of France and England are applicable in their distinct spheres of authority. As a result, there can never be a conflict between international law and domestic law per se; at most there can be a conflict of legal obligations on the part of the state.[488] The validity of any legal act must be assessed separately in accordance with the rules of the relevant sphere — either under the rules of domestic law or international law. If an action violates international law but conforms to domestic law, there is no conflict between the two fields of law.
Each decides legality within its own sphere. Rather, the conflict is one of obligation because the same actor - the state - is required to uphold both sets of rules.Nevertheless, the conflict between these obligations may be particularly acute for the state concerned. For example, as illustrated in the recent decision of the Privy Council in the case of Boyce v R, discussed below, domestic rules might uphold the legality of mandatory capital punishment, on the one hand, and international human rights treaty obligations might render such punishment illegal, on the other. But even in such a case, Fitzmaurice would argue there is no real conflict between the two legal systems per se, since each determines the validity of a legal action under its own rules. The same action can be lawful under domestic law and in contravention of an international treaty obligation.
Fitzmaurice’s viewpoint about the relationship of international law and municipal law is most helpful for our purposes, because it reveals the way in which two different legal orders can coexist and have important consequences for the state, but remain distinct as a matter of law. Such a framework allows us to more clearly and rigorously examine questions regarding the use of international law in domestic courts.
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