1. Introduction -- 2. International law and domestic legal incapacity to give effect to treaty obligations -- 3. 'Original intentions' -- 4. The Role of subnational governments in foreign relations -- 5. The Domestic legal status of treaties -- 6. Fragmented treaty implementation in federal states -- 7. Unified treaty implementation in federal states -- 8. Constitutional guarantees -- 9. Conformity requirements -- 10. Conclusions