Is it only for certain positions or something? I know of Americans who work there, for example, and they aren't on the list.

Edit: I just read the fine print underneath the list:

Staff members, Students and most Fellows recruited by CERN come from the Member States. A limited number of scientists from Non-Member State countries are accepted within the Associates and Fellows Programme.

Romania is a candidate to become a Member State of CERN and therefore Romanian nationals are eligible to apply for Student, Associate and Fellow programmes.

Israel and Serbia are Associate Member States and therefore Israeli & Serbian nationals are eligible to apply for Staff positions as well as Student, Associate and Fellow programmes.