Advanced format ruling
Prevention Star
Card effect (current official text)Equip only to a monster you control, if it was changed from face-up Attack Position to face-up Defense Position this turn. Select 1 monster your opponent controls. That monster cannot attack or change its battle position. When the equipped monster is destroyed and this card is sent to the Graveyard, remove from play the selected monster.
Current rulings for this card are maintained by Konami.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Advanced forum — sourced change requests get reviewed.