How long can the US government detain someone (citizen or not) without proper warrants?
Executive summary
The Constitution’s Fourth Amendment generally prohibits searches and seizures without probable cause and a magistrate-signed warrant, but courts have carved out limited exceptions and federal immigration statutes grant specific warrantless authorities that differ for citizens and noncitizens [1] [2]. In practice, short detentions without a judicial warrant are routinely authorized in criminal and immigration contexts—courts have allowed up to about 48 hours for a probable-cause determination in many civilian arrests, while immigration law and agency policy create a separate framework that can allow longer administrative detention pending removal proceedings [1] [3] [4].
1. What the Constitution sets as the baseline: probable cause and warrants
The Fourth Amendment mandates that warrants issue only upon probable cause and ordinarily protects against entering homes or prolonged seizures without a warrant or equivalent judicial authorization [1]. The Supreme Court has recognized a general limit on warrantless seizures by approving, "as a general matter," short post-arrest delays of up to 48 hours before a probable-cause hearing must be provided—County of Riverside v. McLaughlin supplies the commonly cited 48‑hour rule in federal practice [1].
2. Criminal arrests and the 48‑hour practical rule
For ordinary criminal arrests of citizens and noncitizens alike, the McLaughlin 48‑hour benchmark governs many courts: if an arrested person is held without a prompt judicial probable‑cause determination, detention beyond roughly 48 hours becomes presumptively unreasonable unless the government can show extraordinary circumstances [1]. State statutes and practice vary, but the constitutional ceiling found in case law provides the key federal yardstick [1].
3. Immigration law creates a parallel administrative regime
Immigration law authorizes immigration officers to detain, interrogate, and in some cases arrest without a judicial warrant under statutory provisions such as 8 U.S.C. §1357 and §1226, and those authorities operate under administrative, not judicial, procedures [2] [4]. DHS regulations require that, when an alien is arrested without a judicial warrant, an immigration officer make a custody determination within 48 hours unless emergency or extraordinary circumstances justify additional reasonable time—reflecting an administrative analogue to the criminal 48‑hour rule [3].
4. Detention pending removal can be longer and sometimes mandatory
Under the INA, detention during removal proceedings can be discretionary or mandatory depending on statutory categories; the Attorney General has broad authority to detain aliens pending removal and to revoke release or bond decisions, and courts have struggled over when prolonged immigration detention triggers a bond hearing or shifted burdens of proof [4] [3]. Several federal circuits require a bond hearing if detention becomes prolonged, with some requiring the government to justify continued detention by clear and convincing evidence, but the Supreme Court has not resolved the precise allocation of burdens under INA §236(a) [3].
5. Interior warrantless entries and agency practice: administrative warrants and controversy
Recent agency guidance and memos reported by multiple outlets indicate ICE asserts it may use administrative warrants—issued within the agency rather than by a judge—to enter residences and arrest people with final removal orders, a practice DHS defends as permitted by statute and regulation but one that immigrant advocates say collides with Fourth Amendment protections and established Supreme Court precedent favoring judicial warrants for home entries [5] [6] [7] [8]. DHS has stated Congress has not required ICE to seek judicial warrants in civil immigration cases and points to statutory delegations authorizing administrative arrest warrants [8] [2].
6. Citizens versus noncitizens: different protections and real limits
Constitutional protections apply to “people” generally, but courts have historically treated arriving aliens and certain immigration scenarios differently while still permitting habeas review and some due process protections when fundamental liberty interests are implicated—noncitizens facing removal therefore inhabit a mixed legal space where statutory detention powers can extend beyond the ordinary criminal 48‑hour framework [3] [9]. For U.S. citizens, warrantless entry into a home to arrest is presumptively unconstitutional absent exigent circumstances or an arrest warrant signed by a neutral magistrate [1].
7. Bottom line and where disputes will land
The short answer is: for ordinary criminal arrests, roughly 48 hours is the constitutional touchstone for detention without a judicial probable‑cause finding, while immigration statutes and agency practices permit administrative warrantless arrests and potentially longer detention pending removal—subject to statutory limits, regulations requiring custody determinations, and evolving court challenges over prolonged detention and the use of administrative warrants [1] [3] [4] [5]. Ongoing litigation and political debate will determine how far administrative practices can diverge from traditional judicial-warrant safeguards [6] [10].