Trigger warning: Germans don't understand humor.
You're kidding, aren't you?
von Marwitz
Sadly, he's not. Well, he's kidding about them causing cancer, but not kidding about the not shipping to California for a reason related to cancer.
Basically California has a rather old law (Proposition 65) that requires putting warning labels on things that contain chemicals that might cause cancer. The list of chemicals is ridiculously long and includes many things that you'd have to ingest in vast quantities to have a hope of contracting cancer, but if a product is made with such a chemical (even an inedible plastic box) it is suppose to have a warning label if it is sold in California.
As a result, pretty much anything that is sold in California has one of these warning labels on it because the penalties for non-compliance are higher than just slapping a sticker on the package and possibly losing a few customers scared by the label. In fact nearly every store, including restaurants, in California have a sign someplace warning you the place contains things made from chemicals that might cause cancer. So at this point the law is useless, everything just has a warning label on it in California whether there is any risk or not.
The issue for some online retailers is that they source products from lots of places and some of them may be "drop shipped" (meaning they ship to the customer directly from the manufacturer without ever passing through the hands of the online retailer). So if they drop ship something that is actually made with one of the listed chemicals and the manufacturer didn't put the silly label on it (common thing from China) then they are potentially liable for a fine. So some online retailers have decided it just isn't worth all the hassle of shipping
anything to California because they don't want spend money to track which items in their inventory have listed chemicals and don't have labels on them.