Developers of Open Government Data Mash-ups face the following legal barriers: different licenses, legal notices, terms-of-use and legal rules from different jurisdictions that are applied to an open datasets. This paper analyzes implementation of Revised PSI Directive in EU Member states, also highlights the legal problems. Moreover it analyzes how Public Sector Information is defined by the national law and what requirements are applied to the datasets released by public sector institutions.The results of the paper show that PSI regulation in EU Member countries is very different and the implementation of revised PSI Directive is not successful. These problems limit the reuse of Open Government Datasets.The paper suggests the ontology in order to understand the requirements that originate from the national EU Member countries law and which are applied to Open Government Datasets. Also, the ontology models different implementations of the EU PSI Directive in the Member countries.