https://www.halt.org/booby-traps-and-the-law-defend-your-property/ Above is random link. But I found no end of lawyers stating they are illegal. But they generally don't cite specific laws. The article cites a specific case. Which I believe means, generally, an explicit law doesn't exist because it's covered by other aspects of preexisting tort and criminal law. For example, if you kill someone with a trap, it's murder or manslaughter. A common aspect in force justification is proportionality. As such, I expect the specific charges would vary with the location and specifics of the trap and injury.