It would be completely Legit then however it's highly unlikely to happen. I'm going to Gamestop today however to pre-order Black so I'll download Celebi and let you know.
Ask them if they still have the old johto beast cartridge, and if so, ask them if you can get it. Boom, you now have a legit GAMESTOP celebi
Although my guess is that they shipped it back already.
Who edited my post? Anyways I will ask them if they do just for the sake of it. Also, I still wouldn't consider it Legit.