Laws vary from State to state and even city to city. The best thing to do is simply contact your local police department to see what their take is on the laws where you live. I have purchased several knives online with no problems at all.
Here is advice on buying a switchblade from other WikiAnswers Contributors:
Thailand. I bought one there and got it back through customs without a problem.
For those of you who are not planning a trip to Thailand, you can order them online. Make sure to check your local ordinances so you know what's allowed in your state. many states allow them, some allow you to own but not carry, and a few still consider them illegal completely.
They are illegal
what is a cool pack
It is illegal to sell a switchblade in Delaware, even if you are licensed to sell deadly weapons. Furthermore it is illegal to own or carry a switchblade in Delaware. the closest thing would be a spring assisted open knife. check out Kershaw Knives.
It is not legal. However if you are deployed to a FOB, nobody will care. Some PX's will not sell you a switchblade if you aren't active duty. Others do not care, especially ones staffed by foreign nationals. If you are turned away at the PX, you can get someone from your unit to buy it for you. When you ship stuff home, they search your package for contraband. Best not to have a switchblade inside. http://en.wikipedia.org/wiki/Switchblade covers the legality issues
Switchblade Honey was created in 2003.
Switchblade Valentines was created in 2004.
Strawberry Switchblade was created in 1981.
Switchblade Symphony was created in 1989.
Razer Switchblade was created in 2012.
The Cross and the Switchblade was written in 1963.
Butterfly knives are considered a switchblade under Texas law. A switchblade is a prohibited weapon, meaning that they are illegal to possess. Even if a company will mail you the knife, you can be prosecuted if you are caught with it.
Switchblade Sisters was created in 1975-05.