Why is that the case? Oh, because the definition of "Switchblade" in the Delaware criminal code is unusually broad.
§ 1446. Unlawfully dealing with a switchblade knife; unclassified misdemeanor.You might be able to argue that this statute prohibits only true auto-openers, but I'm not willing to risk it.
"A person is guilty of unlawfully dealing with a switchblade knife when the person sells, offers for sale or has in possession a knife, the blade of which is released by a spring mechanism or by gravity."