If an item is manufactured in one state and shipped to another, it constitutes interstate commerce and federal regulations apply. According to the way that Immigration and Customs Enforcement (ICE) seems to be interpreting the "Switchblade Act" and the way the case law in the 10th Circuit has defined "switchblade or automatic knife," a 'fly is considered an automatic knife. Even if you live in Oregon, where state law allows you to purchase and possess balisongs, if the knife travelled in interstate commerce, you could have some federal "issues." Since Spyderco is abiding by its agreement in the 10th Circuit, and is expecting its distributors and dealers to abide by 10th Circuit rulings, none of the Spyderco autos or 'flys that you saw should have been available for purchase by the general public. Further, Spyderco will not service or perform any warranty work on an auto or 'fly which is not accompanied by the appropriate paperwork, and would be unable to return such a knife to the owner if said owner sent it in without the appropriate paperwork. Spyderco is considering the trainers as balisongs and subject to full regulation. I am unsure if this is due to the legal opinion of their attorney and in order to limit future financial losses, whether this is a stipulation of the agreement that was reached with the 10th Circuit and ICE in order to have their court case resolved, or whether this is in direct response to guidelines and rulings distributed to Spyderco by ICE. I will say that, in the current environment, you may be taking a chance buying an auto or balisong that is not made in Oregon. Will you be prosecuted? Probably not, but there is the possibility. I would stick to items made in Oregon if I were you. My feeling on this issue is that there are eventually going to be more cases involving other knife companies or said companies are going to be provided with some ICE rulings, and that this interpretation of what is "an automatic knife" is going to become the standard for the nation. Alternatively, the 10th Circuit decision may be vacated, either through legistlation or a new court proceeding (though this is less likely than having more regulation, based on my experience in federal law enforcment in the last few years). Having what amounts to widely divergent standards as to what constitutes an automatic knife affecting interstate commerce is completely unsatisfactory, and I wish the whole issue were moot and auto, balis, etc. were legal, at least on the federal level.
Hope this was some help to you, though I know that the answer is disappointing. In my opinion, the whole thing is somewhat silly, but I don't make the law. Currently, I am more concerned with the violent criminals that my task force is targeting. I wish these bad guys were carrying balisongs and automatic knives, and not wearing body armor and carrying 7.62mm x 39mm rifles.
"There is no weapon more deadly than the will." Bruce Lee
"The most pervasive and least condemned form of dishonesty is not doing the best you can." Colonel Jeff Cooper