n.先买（权）；先占

However, the denial made little effect in eliminating the preemption. 然而，国家法律的否定对改变民间交易中的先买权习惯收效甚微。

Of these, the way of imposing had great influence on the existence of the preemption. 对先买权而言，影响最大的就是国家的税粮征收方式。

One controversial preemption issue involves nuclear energy. 一个有争议性的先占权问题也涉及到了核能。

This reluctance to infer preemption makes sense, because the agency can readily adopt an express preemption regulation. 这种不愿意使用先占权的做法是有意义的，因为机构能随时采用明确的先占权法令。