The World Riichi Championship rules were authored by Sylvain Malbec.
Sylvain's goal was to design not only a core tournament rule set recognizable by the majority of players across the world, but also one that would be enjoyable on a more casual level.
It was the result of a survey of significant and current rule sets played across the globe, and with the support of the European Mahjong Association and the Japan Professional Mahjong League.
World Riichi Rules conform to commonly-accepted modern riichi rules. It has been adopted either wholly or with minor variations by international organizations including the Japan Professional Mahjong League and the European Mahjong Association.
For those already playing riichi, the following is a list of major rule points for World Riichi...
Uma: +15 / +5 / -5 / -15
Open Tanyao, Dora, Ura Dora, Kan Dora, Atamahane (headbump), Ippatsu
Kiriage (4-han 30-fu is rounded up to mangan)
Liability payments: Daisangen (Big Three Dragons), Daisūshii (Big Four Winds)
Renhō (Blessing of Man): mangan
Kuikae (swap calling) is not permitted.
Not used: Red fives, agariyame (last dealer ending game if currently the top scorer), kazoe yakuman (capped at sanbaiman), double yakuman, nagashi mangan, open riichi, all abortive draws, tobi (bankruptcy)