As intra-EU labour mobility has increased with successive waves of EU enlargement since the 1980s, industrial relations research has focused on the ways in which these flows have impacted upon the national wage systems and employment regulations of the receiving states (see Berntsen and Lillie, Chapter 2, Cremers, Chapter 9 and Krings et al., Chapter 1, this volume). In such accounts, labour migration typically appears as a challenge or threat to the (usually well-developed) labour market institutions and regulations in the high-wage destination countries. The loss of sovereign control over borders in the EU Internal Market and the questioning of the territorial principle of labour law by European jurisdiction are often seen as fundamental to these issues (Bernaciak, Introduction to this volume).