Is Reject legal in Standard, Modern, and Commander?

Reject is legal in: Modern, Pioneer, Legacy, Vintage, Commander, Pauper, Historic.

Reject

Q: What type of card is Reject?

Reject is an Instant. Its oracle text reads: "Counter target creature or planeswalker spell unless its controller pays {3}. If that spell is countered this way, exile it instead of putting it into its owner's graveyard. *"Grux, for the last time, you have to do more than simply shout 'Apply!' at the administrators." —Pavil, admissions officer*"

Instant

Counter target creature or planeswalker spell unless its controller pays . If that spell is countered this way, exile it instead of putting it into its owner's graveyard.