California is one of more than a dozen US states where marijuana is legal for medical purposes, even though those states' laws are a violation of federal drug policy.
Federal authorities have renewed a crackdown on state-sanctioned medical marijuana facilities despite promises by Barack Obama, the president, to keep the issue low on his list of priorities.
Local authorities are now also trying to stop people from making money off the medicinal cannabis industry, as it is meant to be a non-profit venture.
Al Jazeera's Rob Reynolds reports from Oakland, California.
