Professor Johnstone specialises in Polar law: the governance of the Arctic and the Antarctic under international and domestic law. In January 2019, she publishedArctic Governance in a Changing World (Rowman and Littlefield 2019) with co-author Mary Durfee, a comprehensive introduction to the Arctic from perspective of international relations, international law, and political economy. She has published widely on the rights of indigenous people; international human rights law; governance of extractive industries in the Arctic; international environmental law; due diligence; state responsibility; and Arctic strategies, including the monograph, Offshore Oil and Gas Development in the Arctic under International Law: Risk and Responsibility (Brill 2015).
Professor Johnstone is an active member of the International Law Association and two thematic networks of the University of the Arctic: on Arctic Law and on Sustainable Resources and Social Responsibility. She is the deputy member for Iceland on the Social and Human Working Group of the International Arctic Science Committee. She also services on the advisory board of the Polar Research and Policy Initiative, the social sciences and educational sciences expert panel for the national Icelandic Research Fund (Rannís rannsóknasjóður), and the board of the Equality Fund of Iceland under the Parliament of Iceland.
Professor Johnstone holds a doctorate in juridical science from the University of Toronto (2004), an M.A. in Polar Law from the University of Akureyri (2014), an LL.M. (magna cum laude) in Legal Theory from the European Academy of Legal Theory (2000) and an LL.B. (Hons) from the University of Glasgow (1999).