AB 962 puts several restrictions on retailers who wish to sell ammunition. One of these items deals with the employees that are allowed to have any dealings with the store's ammunition.
12061.(a)(1)
A vendor shall not permit any employee who the vendor knows or reasonably should know is a person described in Section 12021 or 12021.1 of this code or Section 8100 or 8103 of the Welfare and Institutions Code to handle, sell, or deliver handgun ammunition in the course and scope of his or her employment.
Section 12021 describes a convicted felon who is unable to purchase firearms. Section 12021.1 is a list of violent crimes which are felonies. Section 8100 and 8103 describe people who have been " . . . adjudicated by a court of any state to be a danger to others as a result of a mental disorder or mental illness . . . "
Imagine that you're a large retailer like Walmart that no doubt employs a few people who are convicted felons or have been institutionalized. Is it worth the hassle of continuing to sell ammunition and then trying somehow to make sure that the guy in the stockroom with a felony conviction never touches a pallet of ammunition? I think the answer is most likely no.