Mariano Calleja Estellés holds a Bachelor of Laws degree obtained from the Autonomous University of Madrid in 1998, and since 2000 he has specialised in litigation in contentious-administrative proceedings. Mariano Calleja is currently a partner of the law firm of Winkels Abogados and coordinates the Legal Advice for Foreign Nationals Municipal Office of the illustrious Madrid Bar Association, as well as dealing with cases of racism, xenophobia, transphobia and homophobia. In addition, he is the coordinating attorney of the legal services of ANZADEIA, an association that assists victims of human trafficking for the purposes of sexual exploitation.
Prior to this Calleja practised law at the Legal Advice for Foreign Nationals Service of the illustrious Madrid Bar Association during the period 2004 to 2008. In 2005 he also worked as the legal coordinator of the ACOGE Network, Federation of Immigrant Associations.
Thanks to his extensive professional experience, Mariano Calleja Estellés has imparted, directed and coordinated numerous courses in institutions such as the Madrid City Council and at the illustrious Madrid Bar Association, concerning the practice of law as well as in the fields of discrimination and immigration, amongst others.