I don't deal directly with Case, so I don't have any information from them. But, I don't expect it is any type of legal issue on this particular knife. Case is very bad about trying to protect large dealers so they are probably protecting their non-US dealers by prohibiting US dealers from exporting. But, I don't know the specifics.
I will go ahead and say again, that setting up a commercial re-shipper will save international customers a lot of money and grief over time. You can combine shipments, fill out your own customs forms, and be in full control. I realize it seems as if retailers are just making up policies for the sole purpose of randomly punishing people, but sadly there is generally a good reason behind a new policy. You may not like it; but you are not going to be the one bailing the dealer our of jail when the poo hits the fan.