EU officials, temporary agents and contract agents are bound by the EU Staff Regulations. This is the official 'labour code' setting out the rules of their employment, obligations, rights, pension, salary and any other matter concerning their relation with the EU institution or body they are working for.
The reason for the Staff Regulation's existence is the independence these 'agents' or 'servants' enjoy from any governmental or other entity: they are not bound by the labour laws of any EU Member State given their only affiliation is towards the EU institution that employs them.
See also:
Function Groups | Recruitment | EU Officials | EU Jobs | Contract Agent | Temporary Agent