Joseph Harper specialises in the whole field of property law, including land law, landlord and tenant, compulsory acquisition and planning. He is a Fellow of the Institute of Advanced Legal Studies and a Member of the Bar of Antigua. In addition, he is a Member of the Planning and Environment Bar Association and the Chancery Bar Association and a Member of JUSTICE.

He was the Consultant Editor on the Compulsory Acquisition of Land title (2009) and the Planning title (2010) for the Fifth Edition of Halsbury's Laws of England.