Broccoli vs. Health Insurance
You can’t eat broccoli without paying for it. You can get health insurance without paying for it because hospitals are obligated to treat you if you turn up at the ER door. This means society is providing health insurance for free to some people. They are being subsidized by the people who pay for health insurance. There is no such issue with broccoli. Note I am using the phrase health insurance not health care as some of the justices tried to make a distinction between the two.
We can turn heath insurance into broccoli by denying care at the ER door to the uninsured. This is feasible as healthcare services are excludable. Whether society wants to do that are not is a political judgement. Hence, elections are the right mechanism to determine this issue.
Broccoli vs. Wheat
the Commerce Clause of Article I, Section 8 of the Constitution, [gives] Congress the power
To regulate Commerce with foreign Nations, and among the several States, and with the Indian tribes.
How has this been interpreted? Again, via the New Yorker:
In the famous 1942 case of Wickard v. Filburn, the Court said that the federal government’s authority extends to any activity that “exerts a substantial economic effect” on commerce crossing state lines.
The case involved Roscoe Filburn, an Ohio farmer who wanted to grow more wheat than he had been allotted under quotas introduced during the Great Depression to drive up prices. In deciding against Filburn and in favor of the Department of Agriculture, the justices pointed out that the actions of individual wheat farmers, taken together, affect the price of wheat across many states. That is what gives the federal government the power to limit their actions.
This argument can be made for any good, private or public. Hence, the externality argument made above is not necessary under this precedent. Also, Justice Scalia, Roberts etc can be forced to buy broccoli by law.
What is then the limiting principle? The commerce clause has no limiting principle, according to me, a non-lawyer. The limiting principle is the imposed by politics: any politician who seeks to regulate the broccoli market must run for election. This politician will reach the limit of his political career.
(Edit: Changed “eat” to “buy” re broccoli and “free insurance” to “care” re healthcare.)