The division between the two is often not clear and is often politicized in disagreements within a government over a treaty, since a non-self-executing treaty cannot be acted on without the proper change in domestic law. If a treaty requires implementing legislation, a state may be in default of its obligations by the failure of its legislature to pass the necessary domestic laws.
A state party may be in default of its obligations under a non-self-executing treaty if its legislature fails to do what?
pass the necessary domestic laws