The two theories (the doctrinal pair):
1. Dualism (Triepel, Anzilotti, and in practice the British tradition): international and municipal law are distinct legal orders — different subjects (states vs. persons), sources (consent vs. sovereign will), and substance; international law becomes effective domestically only by transformation (an act of the municipal legislature — ratification-plus-implementing-statute). International law cannot pierce the domestic order without its permission; a treaty unimplemented is (domestically) a promise, not a rule.
2. Monism (Kelsen; the continental-and-Latin-American practice in varying degree): one unified legal order — international law above (or within) municipal law; treaties apply domestically automatically upon ratification (direct effect / self-execution), no transformation required. Radical monism (Kelsen): municipal validity itself flows from international law.
The practice — where systems sit on the spectrum:
• The UK (dualist): treaties need implementing legislation (Parliamentary treaty-implementationrule; the classic Mortensen treatment), but customary international law is part of the common law directly;
• The USA: the Constitution makes treaties "supreme law of the land" (Art. VI) — but only "self- executing" treaties apply of their own force (Medellín v. Texas restricting the practice); custom likewise federal common law;
• France, the Netherlands: treaty-superiority monism (treaties above statutes, though below the constitution).
Nepal's position (the paragraph every Nepali answer needs): a moderate dualism: the Constitution of Nepal (2015), Article 279, requires parliamentary ratification for defined treaty categories — peace and friendship, security and strategic alliance, the boundaries of Nepal, and natural resources and the distribution of their uses (by two-thirds of both houses; ordinary treaties by simple majority) — and makes unratified agreements unimplementable; implementing legislation then domesticates obligations (e.g., the statutes passed under the human-rights treaties). The courts' practice completes the picture: statutes are construed in conformity withNepal's treaty obligations (the interpretive presumption), and treaty norms — especially human-rights guarantees — are applied and cited in judgments as interpretive standards, giving Nepal a soft-monist judicial culture inside a dualist constitutional frame. The continuing doctrinal question in Kathmandu: whether ratified treaties should enjoy express constitutional superiority over ordinary statutes (the debate the constitution-drafters visited but the 2015 text left to practice).
The two systems' interactions (the exam's second axis): international law before municipal courts (incorporation, direct effect, consistency presumptions); and municipal law before international tribunals — whose settled rule: Article 27 of the Vienna Convention — a party may
not invoke provisions of its internal law to justify failure to perform a treaty; municipal irregularity is no international defence (state responsibility — Unit 7).