Washington state air rifle laws?

I don't see a restriction as such on their site...

"It is the buyer's responsibility to know and comply with all local, state and federal laws regarding purchase, possession and use in their locality of items such as knives, crossbows, stun guns, laser pointers and chemical sprays. We can not, and will not sell such items to minors. By placing an order for such an item, you acknowledge that it will be used in a lawful manner, that you are of legal age, and that you are not a convicted felon or other adult who is restricted from buying or possessing such item. Before completing your order you will be required to choose whether or not to require an adult signature upon delivery. If you select that option, an additional charge of $5 per package will apply. If you choose not to require an adult signature, you agree that the package may be left without a signature, and you further release Heartland America from any and all liability relating to the delivery of your package. That release includes, but is not limited to, the risk that the package may be stolen or opened by unauthorized persons. "

Cabela's does something similar for black powder weapons: they only ship to a FFL dealer even though there is no requirement to do so - in fact, other black powder gun providers have no problem in shipping BP guns to your door.