Given that the system requires a law to be passed before a challenge in court, this reasoning is inherently fallacious, since if it were true, no law could be ruled unconstitutional.

As far as the US system is concerned that means some forms of limits on the second amendment /are/ constitutional and the 2nd amendment is thus definitively not unlimited unless and until the court issues a ruling that contradicts the previous rulings.

Meaningful and lawful arms controls cannot exist in the US without a new amendment modifying the 2nd.

Then, the subject of the order must fight (at great expense) to regain their rights, which is a de facto presumption of guilt.

No hearing. No charges. No grand jury. No due process.

Due process might be a 30-day order to confiscate guns. If they can't get a grand jury indictment or involuntary commitment to a mental institution in those 30 days, the gun owner gets their guns back automatically and can't be subject to another red flag for 10 years.