law: Indian Trusts Act, 1882 
  77. Trust how extinguished 
  A trust is extinguished- 
  (a) when its purpose is completely fulfilled; or
  (b) when its purpose becomes unlawful; or
  (c) when the fulfillment of its purpose becomes impossible by
  
  destruction of the trust-property or otherwise; or
  (d) when the trust, being revocable, is expressly revoked.