The guidelines on legal pot use issued this week by California Atty. Gen. Jerry Brown offer protection to medical marijuana users and give police the ability to distinguish between criminals and legitimate medical marijuana sellers under state law.

Brown said that formal cooperatives registered under the state’s Food and Agricultural Code or the not-for-profit collectives or cooperatives are legal under the law. But anyone running a for-profit storefront dispensary not operating as either a registered cooperative or collective may be arrested and prosecuted by local authorities, Brown said, according to the Associated Press. Medical marijuana sellers must operate as nonprofit collectives or cooperatives and the products they sell must be grown by state-certified patients or caregivers.

Each legitimate dispensary can grow six mature or 12 immature plants per qualified patient, each of whom need a doctor’s recommendation to smoke marijuana to ease the pain. Brown advised patients who receive doctor’s recommendations to use marijuana to obtain state-sanctioned medical marijuana identity cards. They should be prohibited from using marijuana near schools or at work, unless an employer gives permission.

So far Proposition 215, also known as the Compassionate Use Act, which allows patients to legally use marijuana for medical reasons, did not protect any worker from possible professional repercussions that may come from using the doctor-recommended drug. Brown’s 11-page directive is aimed to clarify California’s medical marijuana law. Advocates of medical marijuana said that they hope the law would offer workplace protection to medical marijuana users. Eleven states have medical-marijuana laws similar to California’s: Alaska, Colorado, Hawaii, Maine, Montana, Nevada, New Mexico, Oregon, Rhode Island, Vermont and Washington.

It is estimated that about 300,000 Americans use medical marijuana.