Yu-Gi-Oh! » Rulings Q&A

Player A controls a face-up "Gemini Elf" and a face-down "Book of Moon."

Player B activates "Soul Exchange," targeting Gemini Elf. After Soul Exchange resolves, Player A activates "Book of Moon" to flip Gemini Elf face-down.

According to modern rulings, Soul Exchange's effect will no longer apply to Gemini Elf. The Battle Phase still cannot be conducted, but Player B cannot tribute Player A's face-down Gemini Elf.

Back in 2010, there were no official rulings for this interaction. How will this be ruled in the Edison Format rated pool?

In Edison Format, Player B can still tribute the Gemini Elf, even if it has been flipped over, as long as it is still on the field at the time of the tribute. Geometry Vibes