The rule discourages dealing tiles that help other players build yakuman.
Sekinin barai for yakuman
If a called tile guarantees a yakuman for the caller, no matter how their hand is won later, the discarder of the called tile is considered liable and will have to pay extra for the win.
If the yakuman is later won by tsumo, the entire value of the hand must be payed by the liable player, including the extra points for honba, as if ron was called against him.
If the yakuman is later won by ron against a non-liable player, this player must pay half the value of the yakuman, as well as the extra points for honba. The liable player must pay the other half of the yakuman.
With rules allowing multiple yakuman, sekinin barai may be invoked on some yakuman while some are scored normally. Payments happen independently for each yakuman. Still, extra points for honba are payed only once. Whenever there are normally scored yakuman among the winning hand, honba payments are conducted normally.
If a player has two open melds of sangenpai, aquiring a meld of the missing sangenpai guarantees them daisangen. If this third meld is created by calling pon or kan on a discard, the discarder is liable for daisangen.
Uncommon rules may invoke sekinin barai on the player discarding into the fourth kantsu of a suu kantsu hand. This fourth kan must therefore be a daiminkan.
Sekinin barai for daiminkan
(To be done, see rinshan kaihou in the meantime.)