An enforcement-procedure concept defining mechanisms used to initiate, litigate, or execute immigration enforcement actions. It governs charging, custody status, hearing structure, and outcomes such as departure, relief, or continued supervision. It does not determine substantive eligibility for unrelated immigration benefits unless separate benefit criteria are satisfied. It materially affects liberty, ability to remain, and the timing and scope of any available relief or review. The concept is generally stable, though procedures and standards may be updated through rulemaking and adjudication over time.