Both challenges raise the question of whether the arbitration clause in the Netherlands-Slovakia bilateral investment treaty (BIT) was valid or whether it violates EU law.

The arbitration between Achmea (formerly Eureko), a Dutch insurance group, and Slovakia concerns a claim for damages under the BIT dating from 1991. In 2004, Slovakia opened its market for private health insurers. Thereafter, Achmea was admitted to the Slovakian market and invested heavily, leading to a market share by the beginning of 2007 of approximately 8.5%. However, due to a change of government in 2006, the liberalisation of the health insurance market was reversed and the rights of the private health insurers restricted. Achmea argued that this amounted to an expropriation and led to damages of more than €60 million. Indeed, in January 2011, the Constitutional Court of Slovakia declared the relevant legislative restrictions to be unconstitutional.

Achmea initiated arbitral proceedings in October 2008 based on the BIT and requested damages from Slovakia. An arbitral tribunal (composed of Vaughan Lowe QC, Albert Jan van den Berg and VV Veeder QC) was constituted according to the provisions of the BIT and pursuant to the UNCITRAL Arbitration Rules with the seat of arbitration in Frankfurt am Main.

In the arbitral proceedings, Slovakia objected to the jurisdiction of the arbitral tribunal, arguing that the arbitration clause in the BIT, consisting of an offer to conclude an arbitration agreement with an investor from the other contracting state, was invalid due to a violation of EU law. Its jurisdictional objection was based on Slovakia's membership of the EU. In particular, Slovakia argued that, under international law, EU law, Slovakian law and German law, its accession to the EU in May 2004 terminated the BIT or rendered its arbitration clause inapplicable and that, accordingly, the arbitral tribunal lacked jurisdiction.

In 2010, the arbitral tribunal rendered an interim award confirming its jurisdiction and rejecting Slovakia's "intra-EU jurisdictional objection" (see Legal update, UNCITRAL tribunal rules Slovak-Dutch BIT not affected by Slovakia's EU membership).

Slovakia then applied to the Higher Regional Court of Frankfurt am Main, requesting the court to set aside the interim award on jurisdiction and to hold that the arbitral tribunal did not have jurisdiction. The court confirmed the arbitral award in May 2012 (see Legal update, Higher Regional Court of Frankfurt confirms validity of arbitration clause in dispute between investor and EU Member State). An appeal is pending to the Federal Court of Justice.

The arbitration proceedings have since been concluded and a final award on the merits was rendered in favour of Achmea at the end of 2012. On 31 January 2013, Slovakia requested the Higher Regional Court of Frankfurt to set aside the final award on the ground (among other things) that the arbitral tribunal lacked jurisdiction to hear the dispute. It is expected that the Higher Regional Court of Frankfurt will postpone any decision until the Federal Court of Justice has rendered its decision on the award on jurisdiction.