There's a strong emphasis on a woman's wali (guardian) during marriage, and when selecting a husband. However, it seems the role of the wali disappears after she is married. In a sense, the husband becomes her guardian, but not in the sense that her husband becomes her "wali" (if I understand correctly).
Question: What role does the wali (guardian) play after a woman is married?
As said in my comment once married the walaya or wilaya (the guardianship) passes to the husband. The father or former wali is only significant in absence of the husband as a person of "trust"!
This is based on verses such as:
...They both found her lord (i.e. her husband) at the door. ...- Translation of Muhsin khan(12:25)
which means that the husband is ruling his household and therefore has the guardianship!
In addition to verses such as (4:34) and (66:6) and the hadith:
"All of you are guardians and responsible for your charges: the Ruler (i.e. Imam) is a guardian and responsible for his subjects; and a man is a guardian of his family and is responsible for his charges; and a lady is a guardian in the house of her husband and is responsible for her charge; and a servant is a guardian of the property of his master and is responsible for his charge." I think he also said, "And a man is a guardian of the property of his father."
(Sahih al-Bukhari, Sahih Muslim, Sunan abi Dawod, Jami' at-Tirmidhi)
