What are the constitutional limits on ICE's authority to enforce state laws?

1. ICE’s baseline authority: federal, not state; grounded in Title 8

ICE is a federal agency whose core powers come from the Immigration and Nationality Act — notably 8 U.S.C. § 1357 — which authorizes immigration officers to question and in some circumstances arrest noncitizens without a judicial warrant (and to act where they reasonably believe a person is unlawfully present and likely to flee) rather than to enforce state criminal codes as a primary mission ^{[1] [6]}.

2. Fourth Amendment limits and warrants: homes, searches, detainers

All ICE actions are constrained by the Fourth Amendment’s prohibition on unreasonable searches and seizures; courts have repeatedly emphasized that officers generally need a judicial warrant to enter private homes absent consent or exigent circumstances, and federal detainers—requests that local jails hold someone for up to 48 hours—are nonbinding and have been the focus of rulings that subject ICE holds to constitutional review and require neutral decisionmakers ^{[3] [7] [5] [8]}.

3. Use-of-force rules and judicial deference

Constitutional limits govern the use of force: federal policy and the Fourth Amendment permit deadly force only when an officer reasonably believes there is an imminent threat of death or serious bodily harm, though courts historically afford on-the-spot deference to officers’ split‑second decisions — a tension that drives litigation after controversial operations ^{[6] [4] [9]}.

4. The Tenth Amendment and the anti-commandeering principle: states can refuse cooperation

Constitutional doctrine bars the federal government from compelling states to administer or enforce federal regulatory programs — the anti‑commandeering rule rooted in the Tenth Amendment — so states and localities may lawfully adopt “sanctuary” policies limiting cooperation with ICE (including refusal to honor detainers) and courts have rejected claims that federal law automatically preempts such local directives in many cases ^{[7] [2] [8]}.

5. What states cannot do: they can’t stop ICE from acting, but can limit their own participation

While states cannot generally prevent ICE from operating within their borders — federal officers retain jurisdiction to execute federal law nationwide — states can withhold cooperation, resources, and information, and pass laws shaping interactions with local agencies; those choices affect ICE’s practical reach but do not eliminate federal authority unless a court intervenes ^{[9] [10] [2]}.

6. Remedies, litigation, and political responses: limits in practice

Legal remedies against ICE are constrained: federal law often limits lawsuits against federal officials, but recent litigation has produced meaningful checks (for example, appellate decisions scrutinizing detainers and requiring procedural safeguards), and states are pursuing legislation to create new enforcement and private‑law remedies or to bar certain federal operatives from local employment — moves that mix legal strategy with political signaling ^{[5] [10] [3]}.

7. Unresolved edges and competing narratives

Several constitutional questions remain contested: how far Congress can condition federal funding without violating anti‑commandeering rules, the precise scope of ICE’s warrantless arrest authority in varied contexts, and the balance between immediate deference to officers’ use‑of‑force decisions and post‑hoc judicial review; media coverage and political advocacy often accentuate either federal supremacy or state resistance, reflecting partisan and institutional agendas rather than settled legal boundaries ^{[2] [1] [9]}.