It's defined in section 1861:

Every person in this state engaged in the business of buying, selling, trading in, or otherwise acquiring or disposing of junk or used or secondhand property, including but not limited to jewelry, silverware, diamonds, precious metals, ferrous materials, catalytic converters, auto hulks, copper, copper wire, copper alloy, bronze, zinc, aluminum other than in the form of cans, stainless steel, nickel alloys, or brass, whether in the form of bars, cable, ingots, rods, tubing, wire, wire scraps, clamps or connectors, railroad track materials, water utility materials, furniture, pictures, objects of art, clothing, mechanic's tools, carpenter's tools, automobile hubcaps, automotive batteries, automotive sound equipment such as radios, CB radios, stereos, speakers, cassettes, compact disc players, and similar automotive audio supplies, used building components, and items defined as cemetery artifacts is a secondhand dealer. Anyone, other than a nonprofit entity, who buys, sells, trades in, or otherwise acquires or disposes of junk or used or secondhand property more frequently than once per month from any other person, other than a nonprofit entity, shall be deemed as being engaged in the business of a secondhand dealer.

So (and my eyes glazed over that huge list of objects) the threshold is "more than once a month"? That sounds... far too broad.

I would hope that it applies to everyone or the law would be miss a portion of the illegal activity they are attempting to capture. Criminals will probably still operate in cash and those that are law-abiding now have to go through the hassle of documentation.

So, the criminal is going to be caught because they documented their illegal activities?

I think this is a case of a law that catches only the innocent.

Well, if it prevents thieves from selling their stolen goods to legitimate dealers and forces them to go to specialist "fences", then the law could certainly help achieve its objective of making life more difficult for thieves.

The question is whether the law does too much to hassle the innocent to make it worthwhile.

Recording cash transactions seems like maybe not too much. Making them impossible/illegal certainly seems to be too much.

It's defined in §1861(A)(1) as "Anyone, other than a nonprofit entity, who buys, sells, trades in, or otherwise acquires or disposes of junk or used or secondhand property more frequently than once per month from any other person, other than a nonprofit entity, shall be deemed as being engaged in the business of a secondhand dealer."

The law seems targeted at pawn shops and the like, but is broadly worded enough to apply to some random person buying stuff off of Craigslist.

In the Spring and Autumn, many sports nuts go through a flurry of second-hand sales and purchases. I’m selling a couple of pairs of mountain bike tires right at this moment, so if I were in LA, I would break the law if I accepted cash for a $25 pair of tires.

Nice!