For instance, there is a definition about the nation's right of preemption in the trading between Japan and gaiban (derogatory expression of foreign countries and foreigners) in Genshi Ryo (regulations of markets and checking stations) of Yoro-ryo (Yoro Code).
例えば、養老令の関市令には外蕃に対する無条件の国家による先買権の存在が記されている。