UL is a private company. There're no laws requiring it or penalizing violations. I would think the only legal consequences would be through civil product liability/breach of warranty claims. Plus, like, losing the certification would mean most stores would no longer stock it.
Many products sold in the United States must be tested in a CPSC-certified lab for conformity, of which UL is the best known. But consumer electronics don’t seem to be among that set, unless they are roped in somehow (maybe for hazardous substances?).
Seems like if you filled your house with non-UL compliant stuff and your house burned down, the first fact would be material to your insurance carrier (you know, the Underwiter to which the UL name refers…)
You might want to do some research on what you can buy and legally plug into your own home. It's more or less you get UL listing, or the product isn't available
