The Ninth Circuit, sitting en banc, has determined that a regulation requiring a U visa applicant to be married at the time of filing the application in order to file a derivative petition for their spouse is inconsistent with the statute. Rather, the spouses must only be married at the time the application is adjudicated for the non-applying spouse to qualify for derivative status.
The full text of Medina Tovar v. Zuchowski can be found here:
https://cdn.ca9.uscourts.gov/datastore/opinions/2020/12/03/18-35072.pdf