President Obama has changed the policy that allows federal prosecutors to pursue those who sell and use medical marijuana, when the state laws permit. At present, only 14 U. S. states have legalized the medical use of marijuana - which means you need a prescription for it, and access to a pharmacy certified to dispense it. This does not relax the laws governing recreational use of pot, so don't head out to your greenhouse and start harvesting a little extra weed to sell, even in a state where medical marijuana is legal