This article studies conflicts in the Swedish Labour Court that have occurred between trade unions and companies concerning the pay and working conditions for European Union migrant workers in Sweden during the period 2004–2010. During this period, unions and employers entered into disputes over: unions’ rights in Sweden to be consulted when a company uses a subcontractor, the definition of an employee (the issue of ‘bogus self-employment’), the application of Swedish collective bargaining agreements to and for workers active in Sweden, how to determine wages for temporary staffing agency workers, and workers’ rights to join a trade union. The article discusses the conflicts in the context of a widespread concern about ‘social dumping’ in the European Union, and in the context of weakening trade unions and institutional change in labour markets.