Sebastián is a partner and a member of the energy, natural resources and environmental law areas and leading partner of the water law department. He specializes in energy related M&A, project development, financing and permitting of energy projects and renewables, general regulatory, pre-emptive environmental assessment, oversight, and litigation. In addition, he is active in climate change issues, electromobility and green hydrogen projects.

He is a board member of the Chilean electric vehicles association (AVEC) and also served as director of the Association of Small and Medium Hydroelectric Companies (APEMEC), and as co-secretary general of the Alumni Association, Academy of American and International Law.

In the academic field, he is Professor of Environmental Law at the Urban Studies Institute department from Pontificia Universidad Católica de Chile and Professor in Environmental Law in the Real Estate Law and Business Diploma, from the same university, both since 2014.