Is Alistair, the Brigadier legal in Standard, Modern, and Commander?

Alistair, the Brigadier is legal in: Legacy, Vintage, Commander.

Alistair, the Brigadier

Q: What type of card is Alistair, the Brigadier?

Alistair, the Brigadier is a Legendary Creature — Human Soldier. Its oracle text reads: "Whenever you cast a historic spell, create a 1/1 white Soldier creature token. (Artifacts, legendaries, and Sagas are historic.) Whenever Alistair attacks, you may pay {8}. If you do, creatures you control get +X/+X until end of turn, where X is the number of historic permanents you control. Power/Toughness: 3/3"

Legendary Creature — Human Soldier

Whenever you cast a historic spell, create a 1/1 white Soldier creature token. (Artifacts, legendaries, and Sagas are historic.)

Whenever Alistair attacks, you may pay . If you do, creatures you control get +X/+X until end of turn, where X is the number of historic permanents you control.