Atty. Ysan Castillo is the Regulatory Counsel of Stratbase. He is concurrently the Secretary General of the Philippine Business for Environmental Stewardship (PBEST), an advocacy group advancing the responsible use of natural resources and protection of the environment.

Upon his admission to the Bar in 2011, he started his career as an Associate at the Chan Robles & Associates Law Firm where he litigated various cases before the different trial courts. Thereafter, he worked at the Upholding Life and Nature, Inc. (ULAN) and represented various indigenous cultural communities and concerned citizens groups before various judicial and quasi-judicial agencies. Then, he had a stint in government as a Legal Consultant at the Legal Affairs Office of the Department of Agrarian Reform.

Atty. Castillo possesses extensive knowledge of and experience working on regulatory issues across the executive branch and attached agencies having jurisdiction over energy and environmental matters. In Stratbase, he works on behalf of clients to navigate and shape complex legislative and regulatory policies. With his background in the energy and environmental sectors, he has spent these past few years helping Stratbase clients design and execute strategies that bring together direct engagement with regulatory agencies and the smart use of networks for congressional oversight.

He earned his Juris Doctor Degree from the Ateneo Law School in 2010. While studying law, he was part of the Board of Editors of the Ateneo Law Journal from 2008 to 2010. Atty. Castillo is now taking up his Master in Environmental Management at the Ateneo De Manila University.

Apart from his advocacy work in PBEST, Atty. Castillo is likewise an Environment Fellow of the Stratbase-ADR Institute and writes regularly for the Institute's column in BusinessWorld.