Mark brings with him a wealth of experience in environmental and planning law, with a particular focus on large-scale infrastructure projects in the housing and renewable energy sectors. He has advised a broad range of domestic and international clients on complex issues including Environmental Impact Assessment (EIA), Appropriate Assessment (AA), the Water Framework Directive, Strategic Environmental Assessment (SEA), Access to Information on the Environment (AIE), and general planning compliance.

In addition to his advisory work, Mark is also an experienced litigator with significant expertise in judicial review and planning injunctions. He is a recognised specialist in health and safety law, regularly advising corporate clients on incident and emergency response, regulatory investigations, and enforcement actions across sectors such as construction, pharmaceuticals, food, technology, and renewable energy.

Mark Thuillier commented: “I’m pleased to be joining the Environment and Planning Group at a time of significant growth and opportunity across the sectors we support. I look forward to collaborating with colleagues and clients on complex and impactful projects that contribute meaningfully to Ireland’s infrastructure and sustainability goals.”

Ailish Finnerty, Partner and Chair of Arthur Cox LLP, said: “We are delighted to welcome Mark to the firm. His extensive experience and deep understanding of environmental and planning law will further strengthen our services in this area. Mark’s appointment reflects our continued commitment to supporting our clients with the highest calibre of legal expertise.”

Prior to joining Arthur Cox, Mark practiced in the environmental and planning group of another major Irish law firm.