Mandatory rules for gun storage are very much a double-edged sword on which opinion varies considerably. There is little doubt though that safe storage is an important issue when it comes to avoiding children (in particular) from easily locating a firearm and then possibly causing harm to themselves or others. However - this latest ruling appears to be a step up from a previous version - from kpbs.org/ :
"Under current state law, gun owners are required to keep firearms in a secure container or disabled with a device like a trigger lock only if they live with a person who cannot legally have a weapon under state or federal law."
It now seems that the ordinance is to be applied to all gun owners whether they have children in their domicile or not, and this where some organizations take issue. Again from kpbs.org/ :
"The proposal's opponents, including the California Rifle and Pistol Association and the San Diego County Gun Owners political action committee, said it infringes on their Second Amendment rights, particularly for gun owners who do not have children living with them."
The opposition to this intrusive obligation is very understandable however, it could also be argued that it is down to all gun owners irrespective of any such laws to be responsible, and this means keeping firearms secure against unwanted access including theft. Perhaps where applicable one of the safest means of 'storage' for a defensive weapon is carry on the person - although this is generally not so much of an option outside of the home in CA! When it comes to self defense, immediate access is all important and things like trigger locks become absurd although some storage mini safes allowing for fast aquisition can be viable if readily accessible.
An issue that is often not promoted enough is that of teaching children about guns and safety at an early age - something which in itself, along with sensible gun security, goes a long way towards reducing the chance of unintended harm by instilling a healthy regard for dangers. Gun security can be considered up to a point a compromise, which should not require extra laws to be imposed on owners when common sense should prevail.