First, no, I don't think continued circulation ex post is comparable to the harm that occurs at the time the abuse physically occurs. My own view is that whatev

First, no, I don't think continued circulation ex post is comparable to the harm that occurs at the time the abuse physically occurs. My own view is that whatever feelings flow from knowing that the images are 'circulating' isn't harm at all. Less personally, lingering negative effects from some event in the form of flashbacks or unpleasant memories are not new instances of harm as a matter of law (for whatever that's worth), and I think it goes beyond straining common sense to use the term 'harm' in that way. But let's assume you're right. You think that pedophiles won't find ways to share content even if every tech company in the world implemented this? You think pedophiles don't and won't have terabytes of child porn backed up on hard disks around the world that will be distributed and circulate for the next millennium and beyond, even if it has to be carried around on USBs or burned to CDs (which aren't exactly amenable to CSAM scanning), and then saved to offline computers? Put another way, even if the internet shut down tomorrow, plenty of pedophiles around the world would continue jacking off to those images and sharing them with their buddies - you don't need the internet for that. Further, even if you could convince me that it's harmful in the sense that I understand the word, I'm not sure I'd ever be persuaded that the amount of harm could be sufficient to outweigh the harms that would result from the scanning itself. Happy to listen, though.