He is a tenured professor of Public International Law and International Relations at the Rovira I Virgili University. Member of the Spanish Association of Teachers of International Law and International Relations, since 1995.
He is also a member of the Board of the Faculty of Legal Sciences of the Rovira I Virgili University; Founding member of the Tarragona Law Center (CEDAT). Director of the University-Business Chair "Tarragona Smart".
He belonged to the promoter team of the Euro-Mediterranean Permanent Forum of Universities and director of the Postgraduate University Specialist in International Cooperation of the 11th Foundation of the Rovira I Virgili University, from 2009 to the present.
Castellá holds a doctorate in Law from the University of Barcelona and a degree in Political Science from the National University of Distance Education (U.N.E.D.). He completed a master's degree in Peace, Security and Defense at the General Gutiérrez Mellado University Institute and the U.N.E.D