She has been visiting Research Fellow at RegNet, Australian National University and Texas A&M University. She researches and teaches in regulatory enforcement, compliance, public policy implementation and street-level bureaucratic behaviour. Dr Nielsen has published in international journals including Public Administration, Administration & Society, Regulation and Governance, and Law & Policy. She has published the following books in Danish (titles translated from the Danish): Price of Dialogue: Informal Rules, Asymmetry of Resources and Discrimination in Regulatory Enforcement (Politica, 2002); and Implementation of Public Policy (with Søren Winter; Academica, 2008). With Christine Parker she has edited the book Explaining Compliance: Business Responses to Regulation (Edward Elgar, 2011).