The nation's right of preemption was asserted by the Imperial Court by either sending people, such as benkan (officials of the dajokan) or kurodo (Chamberlain), assigned to serve as karamono no tsukai (Supervisor of Chinese goods) to the ports of call, or by the government officials (esp. ones of low to medium rank) directly negotiating and purchasing from the merchants based on the detailed list of necessary goods made by the Imperial Court.
その後、弁官や蔵人を唐物使に任じて寄港地に派遣し、あるいはあらかじめ朝廷から送られた希望商品の明細に基づいて大宰府の官人が直接来航者と交渉・購入する形での国家による先買権の行使を行っていた。