With some twenty-five years' experience at the Irish Ministry for Economy, Dr Stuart's professional experience covers the full range of an Economic Ministry's brief, including its regulatory areas and developmental functions. In the early 1990s, Dr Stuart worked at the European Commission in several fields, including Competition Policy, and subsequently was the first Head of the State Aid Department at the Irish Ministry for Economy.

Since 1996, he has worked as an international legal and policy advisor in various capacities in over twenty different countries. In the State aid field, he has contributed to the development of State aid regulatory systems in Albania, Serbia, Montenegro, Bosnia and Herzegovina, Hungary, Estonia, Slovakia, Slovenia, Lithuania, Croatia, Bulgaria, Ukraine, Kazakhstan, Moldova and the Russian Federation. He was appointed as EU High Level Policy Advisor on Public Procurement to the Moldovan Government in 2011.

In addition, Dr Stuart has participated in a range of important international negotiations including those at European Union level and at the OECD in regard to State aid reforms and the international monitoring of public supports to industry. He has also contributed many international conferences and journals in regard to competition law and policy, State aid and subsidies controls, company law, consumer protection and industrial development.