The US constitution does not apply to citizens - it applies to the government.

Citizens in the US are implicitly allowed to do whatever they like, subject to laws that the government enacts. The constitution describes those areas where the government is allowed to pass laws. All other areas are off limits to the government, and left for the people to do as they like. To emphasize the point, the amendments specify certain areas that the government is extra-especially-not-allowed to create any laws about, like speech.

The extent to which this is observed today is quite dubious. There are lots of laws that the US government passes which have little to do with anything the constitution allows them to do - but they kinda hand-wave around that and gesture toward something, like the "commerce clause" or whatnot as justification.

But in theory - for any law passed - it is unconstitutional unless you can say exactly where in the constitution it is explicitly allowed.

* Having written all that, I will add that "government" above means the US Federal government, not all the other ones. State, local, have a lot of latitude to make whatever laws they want, unless a federal law specifically prohibits it.

It's not just US citizens, but per the supreme court "foreign organizations operating abroad possess no rights under the U. S. Constitution". In USAID v. Alliance for Open Society International specifically with regards to the first amendment.

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However TikTok US here is a domestic organization operating domestically merely controlled by a foreign organization operating abroad, which complicates matters. It has rights.

By its wording, no, because it applies to "Congress". Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.

A later amendment is held to have "incorporated" this prohibition against the state governments as well, though that amendment doesn't actually specify anything in particular. ("No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.")

It is frequently argued that some act of the government violates the free speech rights of foreigners living abroad, which is to say that whatever it was the government did fell into the class of behaviors prohibited by the first amendment. People tend to find that argument weird; I don't know what its batting average is.

Summing up, nothing extends rights to foreigners, but since the first amendment is a prohibition on the government rather than a grant of rights to certain protected people, foreigners arguably enjoy equal protection.

The First Amendment enjoins only the US government.

So, usually in a representative democracy (republic or not), the judiciary power is supposed to check and limit the other two (to avoid a tyranny of the majority). You can have that done in two way: with "case law", the only way in some countries (like the UK): basically if a law is enforced against a minority, it will be enforced against the majority. Other countries added a consitution. Its use is to limit the executive and legislative power of the government: the legislative power is supposed to prevent the law/executive order from existing or being executed, and base that decision on the constitution.

TL:DR: no, it doesn't even apply to US citizen, only to US government.

PS: "tyranny of the majority" for some is a definition fascism, i disagree, to me it isn't even proto-fascism, it lack a weird mythos about internal enemies and a few other mythos. It's closer bonapartism, or cesarism at worst. To be clear i think it is a precondition to have fascism (I.E as long as your case law/consitution is enforced for everybody the same way, you aren't a fascist state).

The 1st Amendment applies to US citizens' freedom to read/receive communications from non-US citizens (or i.e. read books by non-American authors). That's not under dispute: the current SCOTUS ruling both acknowledges, and sidesteps, that.

Even if it did, that doesn't matter here, since it's American TikTok users whose speech is being suppressed.

"Code is speech" is absurdly reductionist in most cases.

Yes, the government censoring Tiktok's source code on Github would be a freedom of speech violation, but that's not what this is about, is it? See also: Tornado Cash. Publishing code facilitating money laundering is fine (you'll find the code still on Github!); running said code to facilitate money laundering isn't.

Or to go with an even more extreme example: Writing code for a self-aiming and firing gun is speech [1], running said code on a gun in your driveway isn't.

The fact that we are still debating such basics of the First Amendment here is baffling. This is almost as trivial as the other well-known limitations in my view (shouting "Fire!" in a crowded theater etc.)

[1] At least at the moment, and as far as I know; I think we might see this type of speech being restricted in the same way that some facts about the construction of nuclear weapons are "innate state secrets".

Does this apply for malware? Trojans? Websites that host child pornography?

Or does it just apply to the brainrotting addiction machine that shoves 800 videos a minute at teenagers?

To respond to a comment which has now been deleted:

I don't care about the First Amendment specifically. The US constitution is not magical divinely inspired scripture. I care about the underlying principles of freedom of speech, freedom of thought, and freedom of association, regardless of how well or poorly those are reflected by a specific written law.

You can literally go to any other competing platform and shout the same thing from the rooftops.

> Speech is not being criminalized -- you can say the exact same things on a different forum.

s/criminalized/supressed/ and message still holds true. You can still say the exact same things on a different forum.