He is the author of several books, including Justice and Natural Resources (2017) and A Blue New Deal (2022), the latter of which won the American Political Science Association's 2023 Lynton Keith Caldwell Prize.
He went on to read for a Master of Science degree at the London School of Economics from 1996 to 1997, and then a PhD in politics at the University of Bristol from 1998 to 2001.
[3] In the book, Armstrong offers an account of the concept of natural resource that Clare Heyward and Laura Lo Coco described in 2021 as "the most comprehensive and systematic ... to date".
[3] As the title of the book suggests, Armstrong's account is egalitarian, but he does not call for equal distribution of resources.
[9] Armstrong's Global Justice and the Biodiversity Crisis: Conservation in a World of Inequality, from Oxford University Press, was published in 2024.