Final answer:
The enabling statute for the Environmental Protection Agency preempts state environmental protection legislation, meaning that states are unable to regulate issues of environmental protection on their own, even at a purely-intrastate level.
Step-by-step explanation:
In the United States, the Environmental Protection Agency (EPA) is a federal agency responsible for protecting human health and the environment through regulations. The enabling statute for the EPA grants it the power to preempt state environmental protection legislation. This means that states cannot independently regulate environmental protection issues, even at an intrastate level.