Is Decisive Denial legal in Standard, Modern, and Commander?

Decisive Denial is legal in: Modern, Pioneer, Legacy, Vintage, Commander, Historic.

Decisive Denial

Q: What type of card is Decisive Denial?

Decisive Denial is an Instant. Its oracle text reads: "Choose one — • Target creature you control fights target creature you don't control. (Each deals damage equal to its power to the other.) • Counter target noncreature spell unless its controller pays {3}. *"I've heard enough."*"