Questions of applicability, interpretation and succession of treaties are decisive for resolution of many investor-state disputes. Although States can be bound by treaties under international law, investors are not parties to treaties but still have rights and obligations under international investment law.
Complex issues of treaty law may arise at the stage of entering into effect and application of unratified investment treaties, for example related to the impact of unratified treaties on customary international law and provisional application of unratified treaties, such as the Energy Charter Treaty.
When applying and interpreting international treaties, tribunals also deal with issues of application of investment treaties in the context of territorial changes and armed conflicts. They also rely on the Vienna Convention on the Law of the Treaties and engage other extraneous legal rules and actors for treaty interpretation.
