The commerce clause of the U.S. Constitution is the source of Congress’s authority to regulate interstate economic activity and markets. 

In Wickard v. Filburn (1942), the Supreme Court ruled that Congress may set quotas on an individual farmer's wheat growing capacity. The court reasoned that if every farmer grew over his allotment purely for his own family’s consumption, there would be a substantial economic effect on the market for wheat. 

In U.S. v Lopez, the Supreme Court ruled that regulated activity must be “inherently economic.” In that case, a federal law restricting guns in school zones would not fall under the category of “inherently economic.”

In NFIB, the Supreme Court limited Congress’s power again, saying that Congress may only regulate goods that are already in an interstate market. This reasoning led the Court to conclude that the commerce clause cannot be a source of power for Congress’s individual mandate, which is a central part of the Obama administration’s Affordable Care Act (2010) that levied a nationwide tax on all people without health insurance.

In the future, Congress could use the commerce clause to pass a law mandating vaccinations due to the significant economic effect the COVID-19 pandemic had in 2020. This clause is the root of the power that Congress has on the interstate and intrastate markets. The interpretation of its breadth has not been easily defined and will continue to be clarified in future Supreme Court cases.

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