Federal prosecutors recently sent warning letters to property owners and operators who are suspected of running illegal marijuana stores in several Southland communities, including unincorporated Walnut and La Puente, according to authorities.

The letters are part of an ongoing, coordinated effort that started in the fall to shutter commercial marijuana collectives statewide, according to a news release.  The push has included filing four asset forfeiture lawsuits against properties operating marijuana storefronts in Los Angeles and Orange counties.

One of those asset forfeiture lawsuits was against the building that houses Alternative Medicinal Cannabis Collective in an unincorporated part of Covina.  Letters warning 17 others suspected to be operating included a store in unincorporated Walnut and another in La Puente, authorities said. 

What has been dubbed unincorporated Walnut is outside of the city limits, so it is under the jurisdiction of Los Angeles County. The letters inform the property owners and operators that they are in violation of federal law and have 15 days to take steps to halt the sale and distribution of marijuana at the stores.

Four United States Attorneys in California announced their coordinated effort in October to target illegal marijuana cultivation. 

The use of marijuana for medicinal purposes was legalized in 1996 under the voter-approved Proposition 215, commonly known as the Compassionate Use Act.  In 2003, Senate Bill 420 was passed, which required the State Department of Health Services to set up and maintain a voluntary program for the issuance of identification cards for qualified medicinal marijuana patients. 

Tensions related to enforcement in the past few years have been sparked by the conflict between state and federal laws related to marijuana use.

The California Supreme Court agreed this week to review two local court rulings from Long Beach and Riverside that deal with the conflicting laws, reported the San Jose Mercury News.