This chapter deals with the nature and procedures for permanently modifying the boundary and/or terms of a Crown/Government Lease as a process of changing the content of a land contract between the lessor the government and the lessee for a land lot by mutual agreement. This is protected by the privity of contract, which is generally outside the public law of judicial review’s reach. Apart from the approach to assess the “modification premium”, which is the consideration or quid pro quo that the lessee pays to obtain the lessor’s consent to modify the Lease, this chapter deals with temporary modifications and short-term/temporary waivers.