After studying at the Universities of Oxford and Cambridge, Prof. Reid worked as a lecturer in the Department of Public Law at the University of Aberdeen for 10 years before taking up a post as Senior Lecturer in Dundee at the start of 1991. He was appointed Professor of Environmental Law in 1995. He was Head of the Department of Law from 1997-2000 and served as Dean of the Faculty of Law and Accountancy from January 2004 until a reorganisation of University structures led to the abolition of the Faculty in August 2006. Between 2004 and 2013 he was a member of the Peer Review College of the Arts and Humanities Research Board and from 2010-2013 as one of its Strategic Peer Reviewers. In 2011 he was appointed as a member of the Law sub-panel for the assessment of research under the Research Excellence Framework (REF 2014).  He served for many years as Convener for Scotland on the Executive of the Society of Legal Scholars and became a Fellow of the Royal Society of Arts in 2012.

His two main areas of interest are public law and environmental law, which have come together in studies of judicial review in environmental matters, recent studies of the handling of environmental matters within systems of devolved government and studies of the climate change duties imposed on Ministers. Projects have included examining the evolution of environmental concerns in the regulation of hydro-electric dams (funded by the AHRB) and collaborative work with geographers on the legal issues arising from the dynamic nature of the coastline. A research project with Andrea Ross (funded by the AHRC) examined the implementation of EU environmental law within the devolved structures of the United Kingdom.  Work on the latest edition of his book "Nature Conservation Law" which was published in 2009 has been developed to explore the role of new legal approaches in biodiversity conservation and attracted funding from the AHRC for a project leading to the book "The Privatisation of Biodiversity?: New Approaches to Conservation Law" (with W. Nsoh) and to other publications in academic and professional journals.

The impact of Brexit on environmental law is a further area of interest, leading to appearances at the Scottish and UK Parliaments, involvement in a research project (funded by the ESRC as part of the UK in a Changing Europe programme) and participation in groups seeking to provide information and advice on the technicalities of the process. From 2019 to 2021 he served as an adviser to the Environment, Climate Change and Land Reform Committee of the Scottish Parliament. Work on this topic has produced several conference and seminar papers and articles, one of which won the 2016 Willoughby Prize for the best paper in the Journal of Energy and Natural Resources Law.  He continues as an adviser to the Net Zero, Energy and Transport Committee at Holyrood.

A further ESRC-funded project, "Uncovering the Environment" (joint with Dr. S. Whittaker (Law) and Dr. J. Mendel (Geography)  examined the use and impact of the public right of access to environmental information, leading to the book "Freedom of Environmental Information".

He plays an active part in the environmental law community, including roles as founding Convener of the Environmental Law Section of the Society of Legal Scholars (formerly Society of Public Teachers of Law) and as a member of the editorial boards of Scottish Planning and Environmental Law, the Journal of Environmental Law and Environmental Law and Management. He contributes to the work of the UK Environmental Law Association, of which he is a Patron, especially its Scottish and Nature Conservation Working Groups and Governance and Devolution Group (co-convener from 2021-22) and he is a member of the Environmental Law Commission of the International Union for the Conservation of Nature. 

In January 2014 he was appointed as chair of the Legislation, Regulation and Guidance Group of the Partnership for Action Against Wildlife Crime in Scotland, which brings together the police, land managers, conservationists and the Scottish Government. On several occasions he has given evidence to committees of the UK and Scottish Parliaments and between 2007 and 2013 he was a member of the statutory Public Transport Users' Committee for Scotland.

Within the University he was awarded the College Prize for Excellence in Public Engagement in 2015 and in June 2017 he was awarded a Chancellor's Prize for Outstanding Contributions to Teaching. 

He retired from his full-time post in 2023 but is continuing with many professional and academic activities.

Postgraduate:- Environmental Regulation (LLM)

Undergraduate:- Energy Projects and Environmental Law, Public Law, Climate Change Law, EU Law

Postgraduate supervision can be offered in the fields of environmental and public law. Research students have worked on the effectiveness of statutory obligations to have regard to nature conservation, strategic environmental assessment, coastal issues, the use of the criminal law to enforce environmental rules, conservation covenants and how far the contaminated land regime incorporates a stewardship approach to land ownership.

Other teaching has covered a wide range of subjects including Constitutional Law, Administrative Law, Human Rights, English Criminal Law and Evidence and Legal Research Methods as well as contributions to Legal System, English Law of Property, Equity & Trusts, Private Law of Scotland and to the Induction Programme of the Centre for Energy, Petroleum and Mineral Law and Policy. He has been responsible for the dissertation modules at both LLM and LLB levels.  Prof. Reid is a fellow of the Higher Education Academy.

Environmental Law: biodiversity, nature conservation, regulatory approaches and enforcement, regulation of water resources (esp. hydro-electricity), coastal issues, forestry.

Constitutional and Administrative Law: multi-layered government, devolution, Brexit, subordinate legislation, judicial review, human rights.

Now that he has retired, he is no longer available for research supervision. The work of current and past research students includes the following topics: legal issues arising from the dynamic coastline, a comparison of marine fishing rights in China and the UK, the use of the criminal law to enforce anti-pollution laws in Nigeria, the impact of statutory obligations on public authorities to have regard to conservation, the role of sustainability in the community right to buy land in Scotland, marine governance and contaminated land.