If a card is illegal, it means it cannot ever be used in tournament play or other official Duels. Illegal cards may only be used in casual play at the agreement of all participants. In general, official cards which are illegal can be distinguished by the presence of Limitation Text (most commonly "This card cannot be used in a Duel.") where the passcode would be normally placed, in the card's lower left-hand corner. All unofficial and counterfeit cards are also illegal.