How medical marijuana is transforming the pot industry.

In 2003, the California State Legislature passed Senate Bill 420. The law was intended to clear up some of the confusion caused by Proposition 215, which had failed to specify how patients who could not grow their own pot were expected to obtain the drug, and how much pot could be cultivated for medical purposes. The law permitted any Californian with a doctor’s note to own up to six mature marijuana plants, or to possess up to half a pound of processed weed, which could be obtained from a patients’ collective or coöperative—terms that were not precisely defined in the statute. It also permitted a primary caregiver to be paid “reasonable compensation” for services provided to a qualified patient “to enable that person to use marijuana.”