Guerrilla Tactics | Magic: The Gathering
Formats Guerrilla Tactics is Legal in
Official Oracle Text for Guerrilla Tactics
When a spell or ability an opponent controls causes you to discard Guerrilla Tactics, Guerrilla Tactics deals 4 damage to target creature or player.
Official Rulings for Guerrilla Tactics
10/4/2004 : The second ability will trigger even on an optional discard caused by an opponent.
10/4/2004 : Discarding as a cost to cast a spell will not trigger the ability. Only discarding as an effect will trigger the ability.