Leyline of Sanctity evita que el jugador sea objetivo. Chandra's Defeat no hace objetivo a jugador, así que el Leyline of Sanctity no lo afecta.

Chandra's Defeat
R
Instant
Chandra's Defeat deals 5 damage to target red creature or red planeswalker. If that permanent is a Chandra planeswalker, you may discard a card. If you do, draw a card.

Leyline of Sanctity
2WW
Enchantment
If Leyline of Sanctity is in your opening hand, you may begin the game with it on the battlefield.
You have hexproof. (You can't be the target of spells or abilities your opponents control.)