when we structure environmental law.

要慎重考虑的因素
Another key question, number five,

第五个关键问题
is should we allow preemption?

是否应存在优先权
Preemption is a really interesting idea

优先权是个很有意思的话题
that the federal government could prevent a state

联邦政府可以禁止州政府采取
from adopting regulations that might be different or less restrictive

不同于或宽松于
than the federal standards.

联邦标准
And the Clean Air Act is a great example of this.

《清洁空气法》就是个极好的例子
Because the Clean Air Act does preempt states

因为《清洁空气法》即禁止了州
from adopting regulations that are different from the federal standards

采用不同于联邦标准的法律规范
with respect to vehicle emissions, power plant emissions,

如在汽车尾气排放发电厂排放
mercury emissions.

汞元素排放等方面