alex impey is breaking the law by openly selling marijuana to customers seeking pain relief .
he sells medicinal oil from the drug at about $ 100 a gram and some people use up to a gram each day as treatment .
mr impey also teaches the terminally ill how and where to grow their own .
his `` hemp store '' alone receives more than 20 requests for help accessing medicinal cannabis each week .
patients who contact him include cancer sufferers , those with parkinson 's disease , multiple sclerosis and children with epilepsy .
larisa rule , 3 , is one of his customers , and takes the drug to reduce her seizures .
her father peter risked two years in jail for preparing his own crop .