Riichi (modern Japanese mahjong) was introduced independently in several European countries, and consequently slight differences in the rules existed across the continent.
With the scheduling of the first European Riichi Championship in 2008, the need arose to standardize the riichi rules in the context of the European Mahjong Association. This resulted in the EMA Riichi Competition Rules as standard for Riichi tournaments.
The rules were revised in 2012.
Riichi rule book you can download here
Riichi: Summary of main rules download here
Rule translations of the revised rules are pending. These documents are based on the 2008 edition Here