NRS 453A.310 Affirmative defenses.
1. Except as otherwise provided in this section and NRS 453A.300, it is an affirmative defense to a criminal charge of possession, delivery or production of marijuana, or any other criminal offense in which possession, delivery or production of marijuana is an element, that the person charged with the offense:
(a) Is a person who:
(1) Has been diagnosed with a chronic or debilitating medical condition within the 12-month period preceding his or her arrest and has been advised by his or her attending physician that the medical use of marijuana may mitigate the symptoms or effects of that chronic or debilitating medical condition;
(2) Is engaged in the medical use of marijuana; and
(3) Possesses, delivers or produces marijuana only in the amount described in paragraph (b) of subsection 3 of NRS 453A.200 or in excess of that amount if the person proves by a preponderance of the evidence that the greater amount is medically necessary as determined by the persons attending physician to mitigate the symptoms or effects of the persons chronic or debilitating medical condition; or
(b) Is a person who:
(1) Is assisting a person described in paragraph (a) in the medical use of marijuana; and
(2) Possesses, delivers or produces marijuana only in the amount described in paragraph (b) of subsection 3 of NRS 453A.200 or in excess of that amount if the person proves by a preponderance of the evidence that the greater amount is medically necessary as determined by the assisted persons attending physician to mitigate the symptoms or effects of the assisted persons chronic or debilitating medical condition.
http://leg.state.nv.us/NRS/NRS-453A.html#NRS453ASec300