It’s late at night, I’m still at the office and want to get home, so apologies in advance for vagueness and the lack of cites. IAAL, but I claim no special knowledge in this area. Some of what follows is based on law school recollection. I’m going to use some (obvious, I think) abbreviations.
The question of how broad the Commerce Clause is (or in other words, how far the Federal government can stretch it to justify legislation) has been the subject of numerous U.S. Supreme Court cases. Originally, it was narrowly construed. In the 1930’s, FDR and his allies in Congress passed New Deal legislation which granted expanded and unprecedented power to regulate industry and agriculture to various Federal agencies. They cited the CC as authority. Opponents of the legislation filed suit, challenging this.
Initially, the USSC struck down much of this legislation. In response, FDR threatened to pack the Court by increasing its size beyond the traditional nine and naming additional pro-New Deal justices. Amazingly, the existing Court changed its views and upheld similar legislation the next time it heard a challenge to its constitutionality. This about-face is known as the “Switch in Time That Saved Nine”.
For the next 60 years, the CC was used as a catch-all. The U.S. and essentially all Constitutional scholars interpreted it as allowing just about anything. There’s a case involving Federal agricultural quotas (designed to provide price supports) that was challenged during this era. Opponents found a farmer who grew the commodity in the middle of some state. He claimed that he grew it for personal consumption and asserted, accordingly, that his actions could not possibly affect IC.
He lost. The court (don’t recall if the case was a SC case or not) found that his production of the commodity did affect IC because, if he didn’t grow it, he’d have to buy it on the open market, which is part of IC. Essentially, CC limitations were a joke.
In the last 10 years or so, the pendulum has swung back a bit. In a couple of cases, the USSC has struck down Federal legislation as Constitutionally unauthorized. One involved some sort of Federal safe schools legislation, which imposed special Federal criminal penalties if the offense took place near a school. The CC was cited as the enabling authority. The USSC essentially said that the joke had gone too far, and that the subject of the legislation had no meaningful relationship to IC.