A more thorough explanation:

Gonzalez v Raich is a U.S. Supreme Court case in which the Court held that Congress had the right to outlaw medical marijuana, even in states that had laws expressly allowing it. The Supreme Court, relying upon its earlier decision in Wickard v. Filburn opined that even if an activity is local, it would be covered under the Commerce Clause if it has substantial economic effect on interstate commerce.

For example, if a person grows marijuana for personal use in a state where it is legal, but the federal government outlaws it, that person could still be prosecuted under federal law. This is because the Supreme Court has ruled that even if the activity is local, it can still have an impact on interstate commerce.

This case illustrates the power of the federal government to regulate activities that may seem local but can have an impact on the national economy. It also highlights the tension between state and federal laws, particularly in areas where there is a conflict between state and federal policies.