Stern Proctor

Oracle Text

When Stern Proctor enters the battlefield, return target artifact or enchantment to its owner's hand.

Card Rulings

10/4/2004 If there is an artifact or enchantment on the battlefield (even your own) when this card enters the battlefield, you must return one to owner’s hand. If not, then simply ignore the “enters the battlefield” ability.
10/4/2004 You can cast this card if there are no artifacts or enchantments on the battlefield.