The world's first cannabis college has opened in the US.

Medical marijuana is being grown legally in the college's laboratories in Oakland, California, and the city council is taxing sales of the drug.

Campaigners have said the rest of debt-ridden California should follow their example and legalise cannabis.

College head Richard Lee said the industry is worth an estimated $15bn in California so sales tax alone would bring in $1.5bn,

"We learned with alcohol prohibition in the 1920s that when you make it illegal it doesn't stop people from drinking, it just causes more crime and violence and less respect for law and law enforcement."