(Copied and pasted from a PM I sent to an admin. They haven't answered yet, so I'll ask here.)
"So I bought Pokémon Silver version a few weeks ago on my 2DS. It came with a code for a Celebi you can redeem on Sun/Moon. I don't have one of the newer games and I want to sell the code for TBT. Would that be allowed, or is it against the rules, as I technically had to buy the game to get the code?"