The Ninth Circuit has rejected an asylum claim brought by a Vietnamese citizen based on membership in the particular social group comprised of “known drug users” because the applicant failed to demonstrate that the group was socially distinct or particularized.
The full text of Nguyen v. Barr can be found here:
https://cdn.ca9.uscourts.gov/datastore/opinions/2020/12/21/17-72197.pdf