There are exempted from the taxes imposed by this chapter purchases which are subject to the motor fuels tax imposed by chapter 24, title 63, Idaho Code, and purchases upon which motor fuels taxes have actually been paid and the sale or use of any fuel which is subsequently transported outside the state for use thereafter outside the state. Nothing in this chapter shall be construed to authorize the imposition of a tax on fuel brought into this state in the fuel tanks of motor vehicles or railroad locomotives in interstate commerce.
Idaho Code § 63-3622C