You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Treaty

Context:
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.

Question:
What institution of a party to a treaty must act to fulfill the party's obligations under a non-self-executing treaty?

its legislature