Charity Law
Particularly on issues relating to charities making effective use of property, and the interface between charity law and property law. Warren is interested in the relationships between charities, their property holdings, and the difficulties that arise in managing this relationship.

Social Housing
As a subset of charity law, with a particular interest in the role played by charities in provision and policy to the disadvantaged. Warren has published extensively on the involvement of charities in housing, particularly in relation to the mentally vulnerable, and has carried out empirical research into the experience of charities in this area.

Property Law
General issues, but particularly relating to the boundary lines between property and contractual concepts and landlord and tenant issues.