Wickard v. Filburn, 317 U.S. 111 (1942), was a landmark United States Supreme Court decision that dramatically increased the regulatory power of the federal government.

It remains as one of the most important and far-reaching cases concerning the New Deal, and it set a precedent for an expansive reading of the U.S. Constitution's Commerce Clause for decades to come.

The Court decided that Filburn's wheat-growing activities reduced the amount of wheat he would buy for animal feed on the open market, which is traded nationally, is thus interstate, and is therefore within the scope of the Commerce Clause.

The decline in the export trade has left a large surplus in production which, in connection with an abnormally large supply of wheat and other grains in recent years, caused congestion in a number of markets; tied up railroad cars, and caused elevators in some instances to turn away grains, and railroads to institute embargoes to prevent further congestion.

By the time that the case reached the high court, eight out of the nine justices had been appointed by President Franklin Roosevelt, the architect of the New Deal legislation.

In addition, the case was heard during wartime, shortly after the attack on Pearl Harbor galvanized the United States to enter the Second World War.

[6][7] The decision supported the President by holding that the Constitution allowed the federal government to regulate economic activity that was only indirectly related to interstate commerce.

Justice Robert H. Jackson's decision rejected that approach as too formulaic: The Government's concern lest the Act be held to be a regulation of production or consumption rather than of marketing is attributable to a few dicta and decisions of this Court which might be understood to lay it down that activities such as "production", "manufacturing", and "mining" are strictly "local" and, except in special circumstances which are not present here, cannot be regulated under the commerce power because their effects upon interstate commerce are, as matter of law, only "indirect".

Even today, when this power has been held to have great latitude, there is no decision of this Court that such activities may be regulated where no part of the product is intended for interstate commerce or intermingled with the subjects thereof.

This record leaves us in no doubt that Congress may properly have considered that wheat consumed on the farm where grown, if wholly outside the scheme of regulation, would have a substantial effect in defeating and obstructing its purpose to stimulate trade therein at increased prices.

He made emphatic the embracing and penetrating nature of this power by warning that effective restraints on its exercise must proceed from political rather than from judicial processes."

[13][14] According to Earl M. Maltz, Wickard and other New Deal decisions gave Congress "the authority to regulate private economic activity in a manner near limitless in its purview.

"[15] That remained the case until United States v. Lopez (1995), which was the first decision in nearly six decades to invalidate a federal statute on the grounds that it exceeded the power of the Congress under the Commerce Clause.

The Supreme Court has since relied heavily on Wickard in upholding the power of the federal government to prosecute individuals who grow their own medicinal marijuana pursuant to state law.