From Guns.com:

The $3.5 million referendum will end grandfathering of magazines capable of holding more than 10 rounds, require relinquishment of weapons by those prohibited by the state from legal possession and mandatory reporting of lost or stolen guns. In addition, it would require background checks prior to all ammunition sales – a first for any state.

It is this latter facet that drew particular concern from the group of California’s municipal police chiefs, led by Ventura Police Chief Ken Corney.