BKSS

BKSS stands for "Because Konami Said So". It is a reference to the often-conflicting nature of some rulings from Konami; if a ruling is given for a card that conflicts with those of other cards with functionally identical effects, or with what is stated in the card's effect itself, Judges and players have to follow the ruling, despite the conflicts, because Konami dictated that that is how the card should be played. In simpler terms, if a card has a ruling that contradicts those of other, similar cards, or its own effects, you have to follow them:

"Because Konami Said So."

A good example of this phenomenon exists with the ruling for "Elemental Hero Rampart Blaster". In both the OCG and TCG translations of its effect, "Rampart Blaster" can attack the opponent directly when in face-up Defense Position, regardless of how many monsters the opponent has, at the time. However, despite their own admission to this translation as being accurate, Konami has issued a ruling that states that "Rampart Blaster" can only attack directly by its effect if there are no monsters on the opponent's field. This ruling stands as of currently, even though UDE has amended their ruling to reflect the card's translation. So, even though the card itself says that it can attack directly regardless of whether there's monsters on the opponent's field or not, the opponent's field must be clear in order for it to attack directly in the OCG, BKSS.

Some other well-known BKSS instances (such as a conflict between the rulings of "Demise, King of Armageddon" and "Levia-Dragon - Daedalus" which dictating whether or not they would be destroyed by their own effect if a card effect is Chained to the effect that flips them face-down) were later amended to become more clear and less contradictory, but these are usually well past when the cards were initially released, and are usually done with cards that have rulings that conflict with those of other, similar cards.