Johnson is the founding director of the Acronym Institute for Disarmament Diplomacy, which works with policy makers and nongovernmental organizations to promote nonproliferation and nuclear disarmament by disseminating information and maximizing opportunities in all available fora. As part of this mandate, she edits the organization's in-house quarterly journal Disarmament Diplomacy. Her expertise is in British nuclear weapons policy, multilateral disarmament negotiations, and grassroots activism. From 2004 to 2006, she served as a senior adviser to the Weapons of Mass Destruction Commission chaired by Hans Blix.