Every EU citizen may freely provide services throughout the EU without discrimination on the basis of nationality. On 11 and 18 December 2007 the EU Court decided that the principle of free movement of services is more important that the fundamental principle of the right to strike and can override the latter.
In the so-called Viking and Laval-Vaxholm cases the Court allowed foreign workers to work for lower salaries than those established by local Swedish collective bargaining.
In the Rüffert case in 2008 the Court did not allow public authorities to insist on normal salaries in public contracts. Only formal minimum or generally applicable salaries can be required.
See also Strikes and Four Freedoms.