Family friend was arrested in US 20 years ago and deported to Venezuala, can he come back to the US now?

Possibly. Much more information is needed about your friend including his criminal record and the reason he wants to return. Certain criminal offenses bar someone from ever returning to the United States while others only result in removal or require a waiver to return. You can read more about criminal aliens at http://myattorneyusa.com/criminal-aliens.