Tijn specialises in administrative law, environment and planning and governmental liability.
He advises and litigates on behalf of his clients from the public sector (ministries, provinces, municipalities, water boards), the regulated sector (fossil, wind, nuclear energy, public housing, healthcare, bailiff’s society) and the private sector (chemical industry, project development, building and construction, FMCG, retail).
Furthermore, Tijn specialises in the negotiation and drafting of contracts, and in conflict resolution with public authorities.
Tijn teaches at Utrecht University and in various post academic programs. He is the editorial chairman of Reed Elsevier's Kennisbank Bestuursrecht and editor of Kluwer's Bedrijfsjuridische berichten and Administratiefrechtelijke Beslissingen.