The state of North Dakota covenants with the purchasers and with all subsequent holders and transferees of notes issued by an authority pursuant to this chapter, in consideration of the acceptance of and payment for the notes, that the notes of an authority issued pursuant to this chapter and the income therefrom, and all moneys, funds, and revenues pledged to pay or secure the payment of such notes shall at all times be free from taxation except for estate taxes and taxes on transfers by or in contemplation of death.
N.D.C.C. § 40-33.1-13