Information-flow control is an important element in computer system security, and there has been significant work done in the field by Denning, Volpano, and others. However, most of the work deals with information-flow control inside a single monolithic application. Wide adoption of the Web service architecture and related technologies effectively solved the problem of universal standard of interconnection of independent systems into larger scale system, but largely ignored the problem of information-flow control. This thesis suggests an approach, which allows for information-flow control techniques of the decentralised label model to be applied to distributed loosely-coupled systems based on Web services. The resulting system design is compatible with existing Web service-based systems, and allows for integration of components that do not natively support information-flow control.