You can look at this case in one of two ways.
The first way is the government's way. The defendant downloaded child porn. He's a sicko. He deserves whatever punishment he receives. The trial court sentenced Lynn to 17 and a half years in prison. Entirely appropriate. Could (and perhaps should) have been even more.
The second way would take a different approach. The defendant indeed downloaded child porn off of Limewire. But he says that he was downloading tons of porn, and that he just accidentally downloaded kiddie stuff. A possibility, though maybe he was actively looking for it instead. Regardless, the guy is 21 years old. Not a scumbag. Criminal history I. No record. Sentenced to 17 and a half years in prison. Almost as long as he has been alive. Plus federal supervised release for life. For downloading free stuff the download of which didn't directly contribute to anyone being harmed.
Which of these views you take, I think, affects your resolution of the doctrinal inquiry at issue in the appeal. Lynn moves for acquittal because he says there's no proof that the files moved through interstate commerce, which is an element of the federal offense (and likely a constitutional requirement as well). On the theory -- an undeniably true one -- that it could have been his next-door neighbor's computer he got the files from, or someone in-state; on Limewire, it's almost impossible to tell. So no proof beyond a reasonable doubt.
The Ninth Circuit rejects that argument. Holding that even if this file didn't travel in interstate commerce, it's sufficient to show that the original video was once shipped interstate. Even though that happened long ago and it's not that video, but rather a distinct file, that the defendant is charged with possessing. So the fact that the child was videotaped in a different state is alone sufficient to prove movement in interstate commerce.
The Ninth Circuit's holding, in my view, is motivated by a political belief and a practical reality. The belief is that child pornography is a big problem. The practical reality is that if we require more that what the Ninth Circuit does, it's difficult or impossible to prove guilt.
Now, whether that should matter to the interpretation of a statute -- backed by constitutional dictates -- is a different question. But I think it's clear that it in fact does. Perhaps the Ninth Circuit shouldn't have been as worried as it clearly was, since after all, defendants like Lynn could always be charged under state law. But that wasn't enough. The panel wants the federal law to be effective. It isn't repelled by the sentence. It's not willing to rely on state prosecutions. It's willing do what's necessary in order to make sure the federal law is effective.
One could have different views on whether that's the right approach. But I think, if everyone's honest, that's what's surely transpiring here. Were this not a child pornography case, I'm not at all sure the Ninth Circuit would have the same willingness to manipulate the statutory/constitutional requirement. Maybe it would. But I think it's a lot easier to do so when it's kiddie porn. Which has few defenders. As amply reflected by both the sentence and holding here.