1. Introduction; Part I. Economic Activities v. the Exercise of Public Authority: 2. Free movement: Treaty Provisions and secondary rules; 3. The competition rules; 4. Public constraints on private parties and private constraints on public measures; Part II. The Public Private Interface: Articles 31, 86 and 87-88 EC: 5. Article 31 EC: Commercial State Monopolies; 6. Article 86(1): Public Undertakings, Special and Exclusive Rights; 7. Article 86(2) EC: Derogation for Services of General Economic Interest (SGEI); 8. Articles 87-88 EC: State Aids; 9. Conclusion.