REDU format ruling
Ninjitsu Art of Decoy

Nearest-era rulings (Tengu, Sept 2011) — no REDU-specific archive exists.
Card effect (current official text)Target 1 face-up "Ninja" monster you control; it cannot be destroyed by battle.
Rulings
- If the Ninja is destroyed or otherwise removed from the field by a card effect, Ninjitsu Art of Decoy remains on the field meaninglessly.
- If the Ninja is removed from the field temporarily, or flipped face-down, Ninjitsu Art of Decoy’s effect is no longer applied.
- If Ninjitsu Art of Decoy is active, then Royal Decree is activated and negates Ninjitsu Art of Decoy’s effect, then Royal Decree is later destroyed, Ninjitsu Art of Decoy’s effect is not re-applied.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the REDU forum — sourced change requests get reviewed.