15. The Government may, if it so considers expedient, by a notification, exempt any estate, ¹[ * * *] of which a vested forest forms part, from sale for arrears of Government revenue accruing during the period the control of such forest remains vested in a Regional Forest Officer under sub-section (2) of section 6 or under section 7 or under section 11 or during such part of such period as may be specified in such notification: Provided that where any such estate, share or part is so exempted, all such arrears of revenue shall be the first charge upon the sale-proceeds of such estate, share or part which may be sold otherwise than for such arrears of revenue.