During World Championship tournaments, all cards are automatically set to their lowest allowed status in any region. (For example, a card that is on the Semi-Limited list in one region but the Limited list in another will be Limited on the World Championship banlist, and a card that is Forbidden in one region but Unlimited in another will be Forbidden.)
However, in addition to any cards that are Forbidden on either the OCG or TCG lists, several other cards are also made Forbidden:
Any cards that are not legal in any region, including:
These cards have an undesirable potential to abuse the "sudden death" and time limit rules in official tournaments. The first four cards allow a player in "sudden death" to instantly win by quickly gaining a large number of Life Points during the opponent's turn with a now-irrelevant cost, while the last card allows a player to legally stall by forcing DRAWs until the time limit runs out (see the Tips page of that card for details).