n pertinent part, the amendment provides:
[I]t shall be an exception from the state's criminal laws for any patient or primary care-giver in lawful possession of a registry identification card to engage or assist in the medical use of marijuana, except as otherwise provided in subsections (5) and (8) of this section.
Colo. Const. art. XVIII, § 14(2)(b) (emphasis added). The amendment also specifies