On 21 December 2010, the Irish Competition Authority issued a press release indicating that a purported acquisition by Stena AB of certain assets of DFDS A/S was void because it was implemented before it was notified to the Authority and before a determination was made. The Authority stated that, "it is not acceptable for parties to implement a notifiable merger or acquisition prior to obtaining approval from the Competition Authority. Any such merger or acquisition is void."

Stena and DFDS infringed section 19(1) of the Competition Act 2002 which provides that a notifiable merger or acquisition cannot be put into effect prior to receiving a clearance determination from the Authority (or until the relevant time periods for the Authority to make a determination have elapsed without such a determination being made). A merger will be notifiable if certain turnover thresholds are met or if the merger constitutes a media merger. Section 19(2) of the Act provides that a merger or acquisition is void if it is put into effect in contravention of section 19(1).

The Stena/DFDS acquisition met the jurisdictional thresholds for mandatory notification and was required to be notified to the Authority. Stena completed the acquisition of the assets on 1 December 2010 and informed the Authority of this on 2 December 2010. The transaction was subsequently notified on 17 December 2010. On 14 January 2011, the Authority decided to carry out a full (phase 2) investigation of the merger notification.

Stena also informed the Authority that it had notified the transaction to the UK Office of Fair Trading and had given undertakings to the OFT that the acquired business would be 'held separate' subject to the OFT's review of the transaction. The OFT has since referred the case to the competition commission for further review. The Authority did not consider that the undertakings given to the OFT altered the status of the proposed transaction in Ireland.