Professor Armstrong joined the Santa Clara University School of Law faculty in 1987 and serves on the boards of several community organizations. She is well-published in the areas of housing, racial discrimination, comparative and constitutional law.

Prior to joining the law faculty at Santa Clara, Armstrong practiced public employment law, served as a staff attorney with the Legal Aid Society of Alameda County, and directed the Academic Support Program at Boalt Hall. While she attended University of California, Berkeley, she served as associate editor of the Ecology Law Quarterly.