A private claim wouldn't work unless and until there was actual harm from a guarantee not being honored in a specific case, and then you would just bring a claim for breach of the guarantee, not false advertising.

This is an excellent point. The seller has a responsibility to stand behind the product they sell, but there is also an onus on the buyer to do their homework.

When I was starting to buy vintage and especially pre-war cards, the later of which I had very little knowledge of at the time, if I decided to buy a card slabbed by a tpg, I did much more than simply look at the grade of the card, the card's centering and overall visual aesthetic. I was looking at the slab, itself, searching for signs of tampering. I looked at the card, with the highest resolution possible, searching for things like uneven/wavy edges that would indicate trimming. I did whatever possible to look into the history of the seller, both here, and, if listed, their Ebay store. I asked questions, building a rapport with the member. I'd ask about the history of the card. And once I had the card in hand, I grabbed my loupe, and examined the card under natural, LED and black light.

As a proactive, informed buyer, I cannot completely eliminate risk, but I can do things to dramatically reduce the likelihood that I'll be searching through a spreadsheet of certification numbers. If it's determined that one of the cards I've purchased has been altered, I'll speak with the seller, but I'll also accept a certain amount of responsibility.

Here is the problem, though. Not everybody buying cards has the knowledge our forum members have. They'll see the card graded, and pay a premium price for a card they feel has received an unimpeachable opinion. What if a young kid is collecting cards, and Grandma or Grandpa decides to get their grandson a baseball card for a birthday or Christmas gift? They won't have any clue that there are issues with TPGs, with card doctors. They'll be completely oblivious to the fraud within the hobby. The kid certainly won't know, either, and that card will sit in their collection for years before they stumble across an old article here, or on Blowout. By then, it's too late.

A related example is if, after the sale new information is discovered about the card, that wasn't known nat the time. For example, if a few years after the sale, hobby historians deduce or learn that a card considered and cataloged as being from 1920 was actually made in 1928. Something perhaps relevant for rookie card collectors-- that rookie card may no longer be a rookie card.

I don't believe the seller should be considered responsible for this, even though the card was misdated at the time of sale.

If I sold one of these cards I'd absolutely accept a refund and hope dealers do the same, but understand not everyone may have the funds to make things right.