Case C-384/10: Judgment of the Court (Fourth Chamber) of 15 December 2011 (reference for a preliminary ruling from the Hof van Cassatie van België (Belgium)) — Jan Voogsgeerd v Navimer SA (Rome Convention on the law applicable to contractual obligations — Contract of employment — Choice made by the parties — Mandatory rules of the law applicable in the absence of choice — Determination of that law — Employee carrying out his work in more than one Contracting State)