REDU format ruling
Armed Ninja

Nearest-era rulings (Tengu, Sept 2011) — no REDU-specific archive exists.
Card effect (current official text)FLIP: Target 1 Spell Card on the field; destroy that target. (If the target is Set, reveal it, and destroy it if it is a Spell Card. Otherwise, return it to its original position.)
Rulings
FLIP: Destroy 1 Spell Card on the field. If the card is face-down, look at the card and destroy it if it is a Spell Card. If it is a Trap Card, return it to its original position.
- This card can destroy a Spell Card on either side of the field. So if your opponent has no Spell Cards and no Set Spell or Trap Cards, you must destroy a card on your side of the field. If it is face-down Trap Card you must reveal it to your opponent, and it is not destroyed.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the REDU forum — sourced change requests get reviewed.