Chain Lightning | Magic: The Gathering
Formats Chain Lightning is Legal in
Official Oracle Text for Chain Lightning
Official Rulings for Chain Lightning
10/4/2004 : The player putting the copy spell on the stack controls that spell.
10/4/2004 : The spell copy has all the text and can result in itself being copied.
10/1/2009 : As Chain Lightning resolves, the targeted player, or the controller of the targeted creature, may copy it. The copy has the same text, target, and color of the resolving spell, though the player who's copying it may choose a new target for it. Once that copy is created (or not), the resolving Chain Lightning has finished resolving and leaves the stack.
10/1/2009 : If the targeted creature or player is an illegal target by the time Chain Lightning resolves, the spell is countered. It won't be copied.