See inter alia C-341/05, Laval case para 60, Case C-490/04, para 19., Joined Cases C-49/98, C-50/98, C-52/98 to C-54/98 and C-68/98 to C-71/98.
Glej med drugim sodbo v zadevi Laval (C-341/05, točka 60), zadevo C-490/04, točka 19, združene zadeve C-49/98, C-50/98, C-52/98 do C-54/98 in C-68/98 do C-71/98.