Can I Buy Second Hand Study Materials on Ebay?

Without violating the Code & Standards?

Please forgive the silly question. It’s been 5 years since I last cracked open a CFA text. I seem to recall some discussion on AF years back about this possibly being a violation because there’s no way to prove the materials originated from a legitimate source. I’m interested in purchasing some used mocks from candidates who passed last year, but how can I be certain the materials I’m purchasing aren’t a Chinese rip-off? I think it’s just a scare tactic by the (legitimate) third party providers who’d rather see me pay sticker price for their materials, but I also don’t want to jeopardize my candidacy to save a few bucks.