In 2006 the UK notified the European Commission that it intended to opt out of the Rome I Regulation (593/2008/EC) on the law applicable to contractual obligations. However, responses to a subsequent 2008 Ministry of Justice consultation on whether or not the UK should opt in to (a substantially revised version of) Rome I showed clear support for an opt-in. The Ministry of Justice wrote to the Commission at the end of July 2008, notifying the Commission of the UK's intention to accept and to participate in Rome I, thereby setting in motion the opt-in procedure. In December 2008 the Commission issued a decision (2009/26/EC) in response to the UK's request to accept and to participate in Rome I, confirming that Rome I will apply in the UK. Article 26 of Rome I (which deals with a member state's obligation to notify the Commission of international conventions to which it is a party) will apply in the UK from 17 June 2009. The remainder of Rome I will apply in the UK from 17 December 2009.

Rome I will replace the Rome Convention on the Law Applicable to Contractual Obligations 1980 (the only remaining Community private international law treaty in treaty form). Its objective is to standardise the rules by which the applicable law in contractual claims is determined and thereby extend the harmonisation of private international law in the European Union and reduce the risk of forum shopping.