In the 1935 case Schecter v. United States, involving farming regulations, the court unanimously struck down parts of the National Industrial Recovery Act for overstepping Congress's commerce power. Liberal Justice Louis Brandeis informed one of President Franklin Roosevelt's aides to "tell the president that we're not going to let this government centralize everything."
The next year, the court ruled in Butler v. United States that elements of the Agricultural Adjustment Act, which inflated food prices by restricting supply, violated the 10th Amendment.
After FDR threatened to pack the court with additional judges friendly to the New Deal, the court lost its spine. In 1937, it upheld the National Labor Relations Act – which greatly expanded the power of labor unions and greatly diminished the freedom of contract – under the "commerce" clause.
In Wickard v. Filburn (1942) the justices even upheld the conviction of a man for growing too much wheat on his farm. The court reasoned that even wheat grown solely for private consumption ultimately had an impact on the economy, turning the "commerce" clause into a regulatory rubber stamp.
The "commerce" clause is now interpreted very broadly. Although in United States v. Lopez (1995) the court struck down a firearms law that exceeded Congress's commerce power, it ruled 10 years later in Gonzales v. Raich that federal drug policy overrode California's medical marijuana laws, despite the 10th Amendment.