It is entirely possible for a licensed or unlicensed contractor to change the locks of a property that is bing worked upon in order to keep the owner from moving in until the job is complted and a certificate of occupancy is issued by the governmental entity that is in charge of its issuance.However, for a contractor to do this on a property that he or she does not have an ownership interest in is clearly improper. By changing the locks to a unit owned by another person, the contractor essentially is interfering with the true owner's property rights to the unit and his or her use of it.Such conduct by the contractor could very well get him or her in a situation not desired to be in.