If the state can order tech companies to blacklist apps, the state can order tech companies to add certain sites to their "malicious browsing" filters or order ISPs to IP-block arbitrary hosts. The state simply has no legal authority under which it may ban apps. If the big tech companies roll over for this and say "yes, sir", they'll do anything.
I'm a huge proponent of regulating big tech companies, but all regulation needs to done under the framework of public and universal rules established in advance, not randomly banning individual apps without proof of wrongdoing or a way to mount a defense.
> If the state can order tech companies to blacklist apps
The state absolutely can order parties not to participate in any way with trade prohibited under it's Constitutional power to regulate international trade.
Which includes Presidential directives issued under the International Emergency Economic Powers Act.
No, the state doesn't blacklist programs. Code is speech. Bernstein v. Department of Justice established that [1] in the 1990s. Sure, if you have an app, and you distribute copyrighted material as part of that app, yes, you can be prosecuted under copyright law and be forced (via injunction) to stop distributing that app. But the word "law" is essential: there is a specific rule, set out in advance, which applies to everyone, and for which there are clear penalties. I have seen nobody explain what law TikTok is supposedly breaking.
If TikTok is doing something bad, fine. Make a rule against the bad thing, then ban TikTok on the basis of breaking that rule. You can't just bypass the whole "make a rule" and "show that $X broke the rule" thing and go straight to "punish X". That's called passing a "bill of attainder", and it's such a terrible idea that the practice is specifically banned in the constitution. Now, maybe this situation isn't technically a bill of attainder, but it's the same damned principle at work, and it's still a bad idea.
> You can't just bypass the whole "make a rule" and "show that $X broke the rule" thing and go straight to "punish X".
Yes, as long as the punishment isn't essentially criminal in nature, you can, and it's long been a regularly used tool of foreign policy, under the International Emergency Economic Powers Act. When sanctions are declared against foreign companies or individuals or trade with them otherwise restricted, it's based on declared threats to the country, not general rules that are announced in advance and then the specific individuals involved found guilty in some judicial process of breaking after the rule was declared. It's all by executive finding.
That this particular banning may be legal (and I think that's arguable) doesn't make it good policy (which I strongly believe it is not), because the reasoning behind nulla poena sine lega applies here too. The whole reason we have rules and not a chaos of capriciousness is to make it possible to plan, predict, and invest. A state that arbitrarily punishes international parties for unclear reasons will decrease confidence in all foreign interactions.
I'm a huge proponent of regulating big tech companies, but all regulation needs to done under the framework of public and universal rules established in advance, not randomly banning individual apps without proof of wrongdoing or a way to mount a defense.