Due process

Before the state takes a person's liberty, property, or status, there must be notice, an adequate hearing, counsel where required, and a meaningful opportunity to be heard. These procedural protections are old, and they exist because the alternative — the state acting unilaterally against individuals — has consistently produced injustice everywhere it has been tried. Due process is what makes the difference between a lawful state and an arbitrary one.

The abuses tracked under this ideal include the denial of counsel where it is required, detention without lawful authority or beyond authorized duration, deprivation of liberty without an adequate hearing, the refusal to honor habeas petitions, the bypassing of required procedural protections in immigration enforcement, and extrajudicial state action that punishes without adjudication. The principle applies to citizens and non-citizens alike, in immigration courts as in criminal ones, because the constitutional question is about what the government may do, not about who the target is.

Further reading: National Constitution Center Interactive Constitution — Fifth Amendment, Fourteenth Amendment. Constitution Annotated: Due Process Generally.