Legal Director at CASS International · Court Expert
· Researcher in International Law
A multidisciplinary career combining legal consultancy, expert-witness work, business management and academic research — based in Valencia with an international reach.
About me
A practice built on the integration of legal, economic, administrative and business knowledge — with particular attention to international relations and the workings of European institutions.
Ciril Sokolov Sidorov is a Spanish legal scholar, entrepreneur, court expert and researcher specialising in International Law, European Law, Immigration and Residence Law, Administrative Law and business legal consultancy. He is the director and head of legal affairs at CASS International, an international consultancy firm providing legal, immigration, administrative and business advice to private individuals, families, professionals and organisations.
His career combines legal consultancy, expert-witness work, business management, academic research and experience within Spanish public and municipal institutions. Started in 2015, it has been built on a multidisciplinary logic: the integration of legal, economic, administrative and business expertise in order to provide rigorous support in complex proceedings.
He has worked at the Ajuntament de València (Valencia City Council) and at municipal companies such as Neteja, Manteniment i Servicis de Mislata, S.A., and has completed internships with the United Nations. These experiences gave him first-hand knowledge of how public administration works, of municipal service management and of the principles of International Law.
He currently combines the direction of CASS International with membership of the Council for European Studies and of AEPEJU, with an ongoing doctoral research programme in International Law, and with active participation in humanitarian initiatives — among them the coordination of relief efforts during the DANA floods that affected the province of Valencia in October 2024.
— Academic background
The academic path combines a law degree with three master's degrees, technical training in international trade, specialist expertise in court reporting and doctoral research in International Law currently underway.
Doctoral programme · University
A dissertation examining international legal relations, regulatory systems and the mechanisms of cooperation between States and institutions. Once the thesis has been defended, the official title will be Doctor of Law, specialising in International Law.
University postgraduate programmes · Universities
Three master's degrees covering Immigration and Residence Law, general legal specialisation and expert-witness practice. They provide a transversal approach to professional practice, combining substantive law, analytical methodology and practical application.
Higher Vocational Training · Spanish educational centre
Advanced training in international commercial operations, logistics, cross-border economic relations and the management of commercial activity — an operational complement to legal and economic knowledge.
Faculty of Law · University
General legal training with particular attention to Public and Private International Law, European Union Law, Administrative Law, Criminal Law and Criminology.
Specialised university training · Spanish university
Documentary research techniques, evaluation of evidence, substantiation of conclusions and the methodology required to draft expert reports across their different fields.
— Institutional affiliation
Professional practice is carried out in permanent dialogue with European associations, professional bodies and centres of study. The following memberships — present and past — attest to the institutional framework of the practice.
International academic affiliation
Member of the Council for European Studies, an international academic body devoted to the interdisciplinary study of European politics, society, law and economics. Participation in the CES supports a comparative reading of contemporary legal and migratory phenomena.
Professional accreditation
Membership of AEPEJU reflects a commitment to specialist training, the exchange of expertise between court experts from different disciplines and the development of quality standards in expert-witness practice.
Institutional marks
— Professional track record
A career built on the integration of legal practice, business management, experience of public institutions and international research.
CASS International · Valencia
Direction and coordination of international consultancy projects: mobility, residence, nationality, business activity, International Law and administrative compliance. A combination of legal analysis, strategic planning, business management and practical knowledge of Spanish institutions.
Neteja, Manteniment i Servicis de Mislata, S.A. · Mislata, Valencia
Administrative work in a company linked to the provision of municipal services in Mislata, Valencia province. Additional experience in administrative organisation, service management and the functioning of local public-sector companies.
Ajuntament de València (Valencia City Council)
Work at the Ajuntament de València in administrative roles within municipal government. Direct knowledge of how local institutions function, of administrative procedures, of document management and of the mechanisms that connect public administration with citizens.
Spanish limited liability companies
Administration and management duties across a range of Spanish commercial companies. Experience in corporate administration, process organisation, document management, institutional relations, administrative coordination and the operation of commercial entities.
United Nations
Internships within the United Nations environment, providing direct insight into the functioning of international institutions, multilateral cooperation and the principles of Public International Law.
Independent professional practice · Valencia
Start of independent professional activity in 2015, with progressive specialisation in International Law, Immigration, Public Administration, Business Law and cross-border legal services.
— Practice areas
Full advisory service under the general immigration regime: stay and residence authorisations, modifications, renewals, residency by circumstance, family reunification and residence for international professionals.
Support throughout the acquisition of Spanish nationality by residence, by option, by letter of nature and by naturalisation, including document preparation and comprehensive administrative follow-up.
Analysis of cross-border legal situations, international mobility, the application of European legislation and relations between distinct legal orders.
Advisory work in proceedings before public bodies, preparation of administrative documentation and representation before Spanish, autonomous and local institutions.
Consultancy on company formation, corporate administration, commercial activity, contractual relations, business organisation and corporate governance.
Advisory work on international commercial operations, cross-border projects and business activities with an international dimension, including logistics and commercial organisation.
Coordination of tax and economic questions linked to residence, business activity and administrative obligations, within the scope of the corresponding professional competence.
Administrative and documentary advice on property transactions, contracts, establishing residence and relocation processes to Spain.
Advisory work on homologation, equivalence, academic recognition and administrative procedures relating to foreign qualifications.
Coordination of translations, legalisations, apostilles and the preparation of documentation destined for international proceedings.
Study of documentation, regulatory analysis and the preparation of specialised reports in the fields corresponding to the professional preparation of the practice.
Expert-witness work with specialisations in Criminal Law, the investigation of economic crime and money laundering, criminological profiles and police psychology, as well as real estate and planning expertise.
— Social commitment
The professional path is complemented by active participation in social, welfare and emergency-response initiatives — a reflection of a personal commitment to solidarity and social responsibility.
October 2024 · Valencia
One of those responsible for a humanitarian aid distribution centre in Valencia during the floods caused by the DANA in October 2024. The work included coordinating resources, organising tasks, managing donations and working alongside volunteers and participants in relief initiatives for those affected. An experience that demanded leadership, responsibility, logistical coordination and decision-making under exceptionally complex circumstances.
Humanitarian volunteering
Participation in volunteering and humanitarian cooperation activities linked to the Red Cross, in line with a professional interest in assistance to vulnerable people and in international protection.
International cooperation
Collaboration with UNHCR on activities linked to international protection, human rights and assistance to people in situations of particular vulnerability.
— Publications and research
Legal research and academic outreach on International Law, European Law, human rights, expert-witness practice and international cooperation — including contributions to specialist publications.
Articles and analytical notes published in professional and academic media. Every title opens the full text in the language currently selected on this page.
A systematic analysis of the changes introduced by the reform of the regulations under Organic Law 4/2000, with emphasis on the new interpretive criteria and their impact on proceedings already in progress.
A comparative study of the administrative and judicial criteria applied to the granting of Spanish nationality by residence, with attention to integration scenarios, deadlines and language requirements.
A review of recent case law of the Court of Justice of the European Union on the coordination of national social security systems and on the residence rights of European citizens and their family members.
A methodological proposal for drafting expert opinions in immigration and migration matters, with emphasis on documentary traceability, the structure of conclusions and the technical reasoning that supports them.
— Professional contact
Advice is provided from Valencia, with coverage of proceedings throughout Spain, coordination with correspondents across the EU and a multidisciplinary profile for legal, immigration and business matters.
Professional office
CASS International
Calle Colón 4, floor 3, office 3A
46004 Valencia, Spain
By appointment, Monday to Friday during office hours.
Institutional site
Institutional page of CASS International, the firm whose legal department he directs.
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