A more thorough explanation:

The effects doctrine is a principle in constitutional law that allows Congress to regulate activities within a state that have a significant impact on interstate commerce. The name of the doctrine comes from the fact that the test used to determine whether an activity falls under this principle is whether it "affects" interstate commerce.

For example, if a company in one state is dumping toxic waste into a river that flows into another state, Congress can use the effects doctrine to regulate the company's activities, even though the dumping is happening within one state. Another example is if a state passes a law that restricts the sale of a certain product, but that law has a significant impact on the interstate market for that product, Congress can use the effects doctrine to regulate the state's law.

The effects doctrine is an important tool for Congress to regulate activities that may have a ripple effect on the national economy. It allows Congress to ensure that states are not engaging in activities that harm other states or the country as a whole.