Arbitration — Jurisdiction — Investor–State arbitration — Energy Charter Treaty, 1994 — ICSID Convention, 1965 — Energy Charter Treaty concluded between European Union and States some of which Members of the European Union — Whether provision for investor–State arbitration compatible with European Union law in intra-European Union disputes — Applicable law — Whether including European Union law — Nature of arbitration tribunal

Economics, trade and finance — Investment — Investment protection treaties — Energy Charter Treaty, 1994 — Investor–State arbitration provision — Whether provision for arbitration of investor–State dispute compatible with European Union law in intra-European Union disputes

Treaties — Interpretation — Principles — Relevance of other rules of international law — Energy Charter Treaty, 1994 — Whether provisions on investor–State arbitration should be read as inapplicable to disputes between investor from one European Union State and another European Union State — Whether investor–State dispute resolution provision providing for arbitration compatible with Treaty on the Functioning of the European Union, 2007

Treaties — Conflict between treaty obligations — European Union Member States — Whether obligations under European Union treaties prevailing over obligations under Energy Charter Treaty, 1994 — Express provision on conflict — Energy Charter Treaty, Article 16

Relationship of international law and municipal law — European Union law — Double nature of European Union law as part of the law in force in every Member State and as deriving from an international agreement between the Member States — Relationship between rights accorded to investors under investment protection treaty and principles of European Union law