comment: Unlike UNRWA, UNHCR has a specific mandate to assist refugees in eliminating their refugee status by local integration in the current country, resettlement in a third country or repatriation when possible.
  Palestinian refugees are unique in that they're defined by UNRWA as "persons whose regular place of residence was Palestine during the period 1 June 1946 to 15 May 1948, and who lost both home and means of livelihood as a result of the 1948 conflict."  They later added descendants because they have records from the red cross and others from 1948 (and later the 6 day war) to show residency.  
  UNWRA - no Statute.  Technically it's a temporary program whose mandate and charter gets rewritten every three years.
  UNCHR - has Statute. Charter doesn't change.