Is Defiant Vanguard legal in Standard, Modern, and Commander?

Defiant Vanguard is legal in: Modern, Legacy, Vintage, Commander.

What type of card is Defiant Vanguard?

Defiant Vanguard is a Creature — Human Rebel. Its oracle text reads: "When this creature blocks, at end of combat, destroy it and all creatures it blocked this turn. {5}, {T}: Search your library for a Rebel permanent card with mana value 4 or less, put it onto the battlefield, then shuffle."