The free movement of labour is one of the 'Four Freedoms' of the EU enshrined by the Treaty of Rome. The primary aim is the creation of a single market whereby goods, capital, services and labour can move freely, uninhibited by constraints. This involves the removal of national tariff and non-tariff barriers. However, while states may have joined the EU because potential economic benefits exceeded the costs (Moravcsik 1996), they may have overlooked the consequences of immigration and its implications for society and in particular the labour market. Moreover, while states play a major role in the regulation of the labour market, both trade unions and employers are similarly important stakeholders within this context, albeit often adopting different positi ons with regards to labour mobility.
Trade unions do not contest the free movement of people or immigration per se. They do, however, voice concerns that mismanaged mobility might undermine national social security systems and express concern of a regula tory 'race to the bottom', along with the erosion of their of their power base. Employers, on the other hand, often seek to evade labour standards in order to reduce costs and increase financial returns. They do this at various levels, for example, throug h subcontracting and worker posting along with, when possible, intervening politically to make possible such circumvention (Lillie et al 2007: 561). These and other strategies are particularly evident in the construction sector and have been facilitated b y the adoption (and transposition) of the Posted Workers Directive (1996), the Services Directive (2006), and the accession of twelve new Member States (2004 and 2007), where enlargement presented employers with opportunities while raising challenges to t he trade unions. A number of high profile cases in the European Court of Justice highlight the pressures that are brought to bear on industrial relations systems and unions through the process of globalisation.