His most recent paper, published in Columbia Law Review, explains the immigrant sanctuary movement as indicative of the traditional state and local government response to federal government overreach in the field of police administration. In addition to his scholarship in the area of criminal federalism, Gardner is developing a line of research assessing disparate African American perspectives on the contemporary criminal justice reform movement. His research has been supported by the National Science Foundation, the University of Michigan Interuniversity Consortium for Political and Social Research, the UC Berkeley Institute for the Study of Societal Issues, and the Prison University Project.