They were never not taxable, if you followed the letter of the law. You are supposed to claim it as income when you sell anything for a profit.

And how do you propose making it possible for the authorities to enforce it, on items that do not have a title the way cars and boats do?

On new ones, conceivably, but it would take an impossible amount of cooperation to do it for existing games, and the enforcement costs would outweigh any potential tax revenue. There are orders of magnitude more cars than pins out there.

Just to be on the safe side, better sell your pins for way less than you have into them! To me, preferably!