The Collaborative International Dictionary of English v.0.48:

Occupier \Oc"cu*pi`er\, n.
   1. One who occupies, or has possession.
      [1913 Webster]

   2. One who follows an employment; hence, a tradesman. [Obs.]
      "Merchants and occupiers." --Holland.
      [1913 Webster]

            The occupiers of thy merchandise.     --Ezek. xxvii.
                                                  27.
      [1913 Webster]

WordNet (r) 3.0 (2006):

occupier
    n 1: someone who lives at a particular place for a prolonged
         period or who was born there [syn: resident, occupant,
         occupier] [ant: nonresident]
    2: a member of a military force who is residing in a conquered
       foreign country

Bouvier's Law Dictionary, Revised 6th Ed (1856):

OCCUPIER. One who is in the enjoyment of a thing.
     2. He may be the occupier by virtue of a lawful contract, either
express or implied, or without any contract. The occupier is, in general,
bound to make the necessary repairs to premises he occupies the cleansing
and repairing of drains and sewers, therefore, is prima facie the duty of
him who occupies the premises. 3 Q. B. R. 449; S. C. 43 Eng. C. L. R. 814.