Counter target spell. Ionize deals 2 damage to that spell's controller.
Legalities
Legal
Duel
Brawl
Penny
Legacy
Modern
Pioneer
Vintage
Explorer
Historic
Timeless
Commander
Gladiator
Oathbreaker
Not Legal
Predh
Future
Pauper
Alchemy
Standard
Oldschool
Premodern
Standardbrawl
Paupercommander
Rulings
2018-10-05
A spell that can’t be countered is a legal target for Ionize. The spell won’t be countered when Ionize resolves, but Ionize still deals 2 damage to that spell’s controller.