Property vested in His Majesty for purposes of the government of the Federation shall, save in so far as any otherwise provide, be exempt from from all taxes imposed by, or by any authority within, a Province or Federated State:

Provided until any Federal law otherwise provides, any property sovested which was immediately before the commencement of Part III of thisAct liable, or treated as liable, to any such tax, shall, so long as that taxcontinues, continue to be liable, or to be treated as liable, thereto.