I haven't heard of anything that would cause that... there is no regulation that would prohibit ammo... I wonder if companies elect not to because of the amount of regulated products, which would surprise me because we aren't the only liberal state... that would limit a ton of business.
That's exactly what it is. I have had both Walmart and Amazon refuse to deliver air guns or pellets to my address is Washington state. I think some companies don't feel it's worth the possible hassle. This could be an intended side effect by anti-gun people in our state govt.