Thanks for the analysis. I am not sure who had the greater proprietary claim over the cards...hence my opinion that someone who is an expert on the law should be involved first. As you write above, there are some maybes and mights.
That being the case, even though it's reasonable to assume that WotC got legal advice, from the point of view of the customer, a letter from WotC legal explaining the situation, with relevant law citations, seems more appropriate than a surprise visit from the Pinkertons. Lets him know due diligence has been done.
I'd agree with that second-last sentence. On the other hand, if - from WotC's perspective - time is of the essence (ie trying to control what they regard as a leak), and if they have already sent messages and received no response, then a physical visit might be seen as the appropriate next step.
I don't know what was in the messages that WotC sent. I do get the impression that perhaps this youtuber was not just a naive customer - that perhaps he knew that he had received the cards in error, and perhaps was deliberately not responding to WotC's communications in order to not expose his own position to attack. But that's just conjecture, based on the small amount that I've read.
I don't know enough about the general character of the serious MtG market to know how outrageous or not WotC's actions were, so I won't conjecture any further than I've done in this post. I really just wanted to reply on the legal aspect, where (as I've said) I don't know the answer, but I can see how it could be quite a bit more complex than some posters have asserted.
I am going to say one other thing, that is also legally oriented and is striking, and a bit ironic, to me: many of the critics of WotC re the Pinkerton's are also strong advocates of the OGL (and so critics of WotC in relation to that matter too). But for the OGL or for that matter CC, to work, then (to speak roughly) a contract between A and B needs to generate binding consequences between A and C, even though C is not a party to A and B's contract. Which is, at least (very) roughly, the same thing as might be involved in the MtG scenario, where the terms of the distribution contract(s) generate legal consequences for the youtuber despite the latter not being a party to the distribution contract(s).
In other words, I'm not sure that some of WotC's stronger critics have a coherent theory of the private law. To some extent, they seem to approach WotC's conduct as if WotC were a trustee for the public of D&D (and its other IP), rather than a commercial publisher.
www.enworld.org
You can feel free to assume it into existence, of course, but then...look, this thread has become about people who always harp negatively ignoring facts in evidence or assuming facts not in evidence, so...wouldn't that be doing the same?
