Read up on the National Emergencies Act.

The federal government can do so, once the President has declared a state of emergency (which, he has).

Is this act actually constitutional? It's not interstate commerce, and I'm having trouble recalling relevant emergency provisions in the constitution that would expand federal authority to local issues. I can imagine the Supreme Court ruling that it's a common-sense provision if someone tries to legally challenge it, but I'm not aware of the history.

The commerce clause cannot be used to abrogate fundamental individual rights, people are seriously misunderstanding what can be done under that clause. There is a mountain of Supreme Court precedent that covers this explicitly, and the specific case of freedom of travel, and also covers attempts to use regulatory technicalities to do the same. The right of Americans to travel freely absent narrow circumstances requiring due process is settled law at this point. This may be inconvenient for anyone that wants to implement a lockdown but this is well-trod legal territory.

I think people are also conflating what the Federal government can do, which is very little, and what local governments can do, which is considerably more. Broadly speaking, the Federal government operates in an "advise and support" role, the legal authority resides with the States and localities. This is an example of where State sovereignty becomes very obvious. But even with the States exercising their broader powers, they are still restricted from violating fundamental Constitutional rights like freedom of speech, assembly, travel, etc.

Supreme count precedent only matters once a court case makes it to court.

Until then, the President of the United States can make an order, and if it is enforced by local authorities, it's defacto legal for the duration.

Not at all. Violating well-established legal precedent that has already been reviewed by the Supreme Court is an easy basis for the courts to place an immediate injunction of the effects of those orders.

This happens in many other contexts, there is no reason to believe it wouldn't happen here.

There is one big reason why the supreme court wouldn't overrule a quarantine order.

You'd be surprised as to what constitutes interstate commerce. I've seen local criminals brought up on federal Hobbs Act charges for their participation in robbing convenience stores. The prosecutor made sure to note that the store was "known to engage in interstate commerce." Almost any business you can think of engages in interstate commerce. Think about it, where does the stock for the store come from? Where were the registers used to process transactions manufactured? Does the business purchase digital advertising? All of those are interstate commerce.

I'm not surprised, because I'm already aware the umbrella is rather larger than most people would expect. Nevertheless, it simply won't cover everything that we'd need covered from a public health perspective. So what happens here?

That only means the federal government can pass a law about it. It doesn't mean they can pass a law that abrogates other constitutionally-protected rights.

Freedom of assembly is our first amendment right. I’m not saying a ban doesn’t make sense but it needs to be by the book.

Public safety exceptions to the freedom of assembly are routine and common.

Freedom of assembly to petition the government for redress of grievances. I believe that is the only freedom of assembly we are guaranteed.

I think you missed the "and to petition":

> or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.

The federal government can claim it affects "interstate commerce".

There is substantial Supreme Court precedent regarding this, Americans have a Constitutional right to freedom of travel on par with freedom of speech. Exceptions are extremely narrow and limited. I don't think people here realize how many times this has been reviewed by the court in cases the government deemed exceptional. This is not new territory legally.

The interstate commerce clause is fundamentally restricted in scope such that it does not violate fundamental individual rights i.e. you cannot use the commerce clause to restrict free speech.

The federal government used the commerce clause to restrict a farmer from growing wheat, and won in the supreme court.

Yes, it was terrible precedent but it also has no relevance here. If you could abrogate fundamental rights with the commerce clause then those rights effectively don't exist and the Supreme Court has consistently ruled on this. You can't use the commerce clause to infringe on the right of free speech, the right to bear arms, etc. This has been argued in the court many times and the outcomes have been one-sided in favor of the individual right.

Freedom of travel -- what we are talking about with a "lockdown" -- is a thoroughly adjudicated fundamental right per the Supreme Court. Using the commerce clause to restrict travel in various ways has already been rejected by the Supreme Court, repeatedly.

Well then we're screwed :(

But wait, haven't there been quarantines during past epidemics?

I mean, what if it's like a hundred people gathering in one place just to hang out? Or do you mean they should just make some baseless argument and let someone who cares sue later?