Legal Bases and Problems of Functioning of the Trans–Caspian Route as an Element of the INSTC

The article examines the international legal framework and the main problems affecting the functioning of the Trans-Caspian route as the “middle” branch of the International North – South Transport Corridor (INSTC). The study aims to identify the applicable treaty-based and institutional arrangements governing carriage and port operations in the Caspian basin and to reveal legal bottlenecks that undermine transit efficiency. The research relies on formal-legal and comparative methods, including an analysis of international agreements, national regulations of the participating states, and doctrinal approaches to the concept of international transport corri-dors. The findings demonstrate that the regulatory environment remains fragmented: tariff policies, customs and transit procedures, border crossing rules, port dues, and ferry operations lack uniformity; coordinated digi-tal solutions (including a single-window model) and effective monitoring/dispute-resolution mechanisms are insufficiently developed. The paper also highlights how external economic restrictions increase legal uncertain-ty for transit and weaken investment safeguards. The author argues for harmonizing national regimes, formal-izing mutual recognition of documents and data, expanding digitalization of transport documentation, and more consistent implementation of international standards on navigation safety and environmental responsibility in port governance.