Advocate General Jääskinen has delivered an opinion concluding that obligations entered into by Slovakia before it ratified the EC Treaty cannot be affected by that Treaty and that, as such, Slovakia cannot be held to be in breach of its obligations under Directive 2003/54/EC concerning common rules for the internal market in electricity. Advocate Generals' opinions are not binding on the Court of Justice of the European Union (ECJ), but are often followed.

On 5 October 1990, Slovakia and Switzerland entered into an agreement to promote the reciprocal protection of investments (investment protection agreement). On 27 October 1997, a Swiss company (Aare-Tessin AG für Elektrizität (ATEL)) and a state-owned network operator in Slovakia (Slovenská elektrizačná prenosová sústava) entered into a contract whereby ATEL paid over half of the construction costs of an electricity transmission line from Poland to Slovakia, in return for priority access to the line for a non-renewable period of 16 years.

The Directive came into force on 15 July 2003 and had to be implemented by member states no later than 1 July 2004. Slovakia joined the EU on 1 May 2004. Article 9 of the Directive provides that each transmission system operator will ensure non-discrimination between system users. Article 20 provides that member states will ensure the implementation of a system of third party access to the transmission and distribution systems applied objectively and without discrimination. The European Commission sought a declaration that Slovakia had failed to fulfil its obligations under Articles 9 and 20 of the Directive because the contract meant that Slovakia was not ensuring non-discriminatory access to the electricity transmission network.

In his opinion, Advocate General Jääskinen considered that the priority treatment afforded to ATEL under the contract amounted to discrimination within the meaning of the Directive. However, a failure by Slovakia to uphold the provisions of the contract would amount to:

Having determined that the priority treatment amounted to discrimination, the Advocate General then considered whether such discrimination was justified. In this connection, Slovakia relied on its obligations under the Energy Charter Treaty, arguing that the EU is legally bound by the obligations of the fair and equitable treatment and non-expropriation contained in it and resembling the substantive provisions of the investment protection agreement. The Advocate General disagreed, noting that the general provisions of the Energy Charter Treaty could not override the detailed provisions of the Directive.

Furthermore, the Advocate General referred to Article 307(1) of the EC Treaty (now Article 351 of the Treaty on the Functioning of the European Union), which provides that the rights and obligations arising from an agreement between a member state and a third country concluded before the date of accession of the member state are not affected by the provisions of the EC Treaty. Applying Article 307(1) to this case, he concluded that Slovakia would be in breach of its obligations under the investment protection agreement if it applied the Directive and did not follow the terms of the contract. Those obligations, which were concluded before the EC Treaty entered into force, could not be affected by the Treaty. As such, Slovakia could not be held to be in breach of its obligations under the Directive.

The application of Article 307 of the EC Treaty justifies the outcome in this case, but at first glance it appears at odds with the idea of market liberalisation the Directive aims to promote. However, in reaching his conclusion, the Advocate General noted that his opinion is not incompatible with the derogation provisions in Article 24 of Directive 96/92/EC concerning the internal market in electricity and Article 7 of Regulation (EC) No 1228/2003 on conditions for access to the network for cross-border exchanges in electricity, allowing investments in the electricity field to be granted temporary privileged access in exceptional circumstances. He also added that there is no threat to market liberalisation since ATEL is a third country company, not an incumbent monopoly with a right that was acquired before Slovakia's accession, fixed in time and not renewable.

Case: European Commission v Republic of Slovakia [2011] EUECJ (Case C-264/09) (15 March 2011).