The United States v. Wrightwood Dairy Co., 1941, was a case that revolved around the constitutionality of federal price controls on intrastate milk sales. The Wrightwood Dairy Company argued that these regulations were unconstitutional as they exceeded Congress's power under the Commerce Clause because they regulated activities within individual states rather than interstate commerce. However, the Supreme Court unanimously ruled in favor of the U.S government stating that even if an activity is purely intrastate, it can still have such a substantial effect on interstate commerce to be within federal regulatory power. The court held that Congress had rightfully exercised its authority under the Commerce Clause when it enacted legislation regulating prices for milk sold by producers and handlers operating entirely within one state since this could directly affect interstate commerce.

In the United States v. Wrightwood Dairy Co., there was no recorded dissenting opinion. The Supreme Court's decision in this case was unanimous, with all justices agreeing that Congress had the power to regulate intrastate transactions if they have a substantial effect on interstate commerce. This ruling upheld the constitutionality of federal price controls on milk set by the Secretary of Agriculture under authority granted by the Agricultural Marketing Agreement Act of 1937, even though most milk sales were local and did not cross state lines.