Can the Advanced Threat Containment Unit (ATCU) put people exposed to Terrigen Crystals in suspended animation? There are a host of issues with freezing people, but the ATCU has justified the practice on the grounds the Inhumans are “sick,” thus require being placed in suspended animation until they can be cured, out of the need for public safety.
The Marvel Cinematic Universe has a precedent for placing prisoners in suspended animation. The Abomination was frozen, likely given the complexity it would take to imprison him. It was never stated whether the Abomination had a trial, but there was no question he went on a killing spree in New York City.
People exposed to Terrigen Crystals in fish oil are in a very different category. In states such as California, a peace officer must be able to point to specific and articulable facts that a person has a mental disorder and is a danger to themselves or others to place them on an involuntary hold for 72-hours. Cal Wel & Inst Code § 5150.
Placing people with infectious diseases in quarantine is a legitimate exercise of police power. Compagnie Francaise De Navigation A Vapeur v. Louisiana State Bd. of Health, 186 U.S. 380, 387-388 (U.S. 1902). However, that requires people have a disease that can be passed on to others. Having super powers is certainly a condition, but not a transmittable disease.
A school can send a student home if the student has lice to prevent the spread of the parasites. Being an Inhuman could be similar, expect instead of bugs living in your hair, you breathe fire. There is no special shampoo for breathing fire.
The ATCU is holding people against their will, without a trial, in suspended animation. The ATCU does have an argument that people who suddenly have powers are a danger to those around them that does require treatment. However, being an Inhuman is neither a disease nor a mental disorder that means they are a danger to others. A new Inhuman might not be able to control their powers, but that does not mean they have engaged in conduct warranting being held against their wills.