The Warrantless Arrest

Introduction The government cannot always require a judge to sign a warrant before removing a suspect. Therefore, one has to consider in what cases the government is allowed to use its authority without a warrant.

There is a controversy in the current Southern California case, one that was intervened by the US District Court Judge Maame Ewusi-Mensah Frimpong on September 2, 2026. For any further warrantless arrest of immigrants, she ordered immigration officers to firstly ascertain if the immigrant would escape if they went to get a warrant and document the facts that show probable cause.¹ One should understand the issue in context: When can the government take a person into custody without a warrant?

The Fourth Amendment’s Basic Rule

The Fourth Amendment of the United States Constitution provides that persons cannot be subjected to unreasonable searches and seizures and that warrants shall issue only upon probable cause and particularity requirements.²

Arrests are a form of seizure, although the US Supreme Court has decided that they are not always searches. The Supreme Court in United States v. Watson noted that there is nothing in the Fourth Amendment that prevents law enforcers from making an arrest in public places when they have probable cause.³ That being said, the Fourth Amendment does not allow every warrantless arrest.

The government would need probable cause and grounds to lawfully detain a person and specific statutes might stipulate further requirements for law enforcement. This consideration applies to immigration enforcement as well.

Congress Added a Statutory Limit

A legislative provision on immigration offers a standard that immigration officers should use to determine if a warrantless arrest is allowed. There is a clear distinction between probable cause for committing a violation and probable cause for making a warrantless arrest.

It is important to note that while the former provides the rationale for an arrest, there should be further justification for arresting a person without a warrant. Therefore, there is a fundamental difference between the two forms of probable cause.

The Flight-Risk Question The immigration officers should consider the condition of likelihood of escape before making a warrantless arrest. Thus, the government would need probable cause to show that a person is illegal or removable and that the person is likely to escape if a warrant for his arrest is issued. One should understand that the two considerations are separate assessments with different rationales. The issue is raised in context of the litigation in Southern California.

It is argued that in most cases, immigration officers make warrantless arrests without first considering whether a person they arrested had the likelihood to escape before a warrant was issued.

Judge Frimpong ruled that practices do not conform with the statutes and ordered that immigration officers assess the likelihood of escape before making a warrantless arrest. That litigation shows that a warrantless arrest may sometimes be lawful depending on the prevailing circumstances.

Immigration Enforcement and the Fourth Amendment One example of such a law was given by the Supreme Court in its ruling on searches conducted at the international borders.

In Almeida-Sanchez v. United States , it held that a warrantless search conducted 25 miles north of the Mexican border was unreasonable because the Coast Guard did not have probable cause for the search even though it had the authority to conduct such a search at the nation’s border.⁵

It can be seen that while warrantless searches conducted by law enforcers within the nation’s borders are unreasonable, those conducted at international borders are lawful.

Similarly to warrantless searches conducted at borders, an immigration officer’s warrantless arrest of an illegal alien may be lawful by virtue of one’s immigration status if one evades capture. The government has more authority to control foreign nationals and may have probable cause to believe that removable aliens will evade its officers’ custody if a warrant is issued for their arrest.

Arrests Are Not Searches Another aspect of warrantless searches is that they are considered legal whenever they meet standards of reasonableness. There are other Fourth Amendment protections that apply to searches conducted within interior of the United States .

As has already been mentioned, one needs to distinguish between a search and an arrest.

Almeida-Sanchez was a case concerning a search while the Watson case is about an arrest. Generally, arrests require probable cause of a crime, although that requirement may be waived under certain circumstances.

The Government's Interest Federal immigration officers have specific authority to enforce federal immigration laws: They have to consider whether their arrest is lawful. The legal analysis that a court conducts in reviewing a warrantless arrest can depend on several aspects.

A court may consider whether there is probable cause that a crime has been committed. The government has authority to arrest a person who violates immigration laws. It is also needed to review what immigration laws apply to a specific set of circumstances in order to determine if a warrantless arrest is lawful. It has been said that there is no single test that determines if a search is lawful.

However, in analyzing a search, the government’s interest may be weighed against the harm done to the victim in order to determine if a search is lawful. Such a standard does not exist in analyzing an arrest.

There is probable cause that a crime has been committed and an arrest is lawful. The United States Supreme Court in Gerstein v. Pugh held that the constitutional standard for determining if an arrest is lawful requires probable cause that a crime has been committed by the accused.⁶

Federal statutes regarding immigration provide further criteria for immigration officers while police officers are subject to constitutional law. This implies that a court may consider both US Constitution and federal immigration statutes.

A distinction needs to be made between the constitutional requirements and statutory requirements for warrants for arrests. A warrantless arrest could raise constitutional issues when a warrant is needed and not needed when it would otherwise not be necessary.

A similar argument applies to the immigration statute of 8 U.S.C. § 1357(a)(2) as well. One must recognize that a warrantless arrest raises a question of its own. There is a government interest in having government officials remove illegal aliens from the United States.

Federal immigration officers cannot obtain a warrant whenever a warrant is issued. A reasonable alien may leave before a warrant is issued. Congress provided that statute for a reason. It recognizes that a warrantless arrest may be needed for removal of aliens. In addition, a warrantless arrest is more practical when it comes to immigrants.

The Individual's Interest

The issue of government interest applies to individuals as well. Taking a person into custody by force is one of its most severe powers.

This is why the Fourth Amendment allows it only when it is reasonable for the government to do so. Any government action involves a government interest as well as an individual’s interest.

It is evident that the government has an interest in enforcing its immigration laws and ensuring that aliens are in order with its laws. The question, however, is about whether such government conduct is reasonable and lawful.

Why Documentation Matters When it comes to documenting one’s actions, it may help in cases where a person questions officers’ authority to make a warrantless arrest. It will be necessary for officers who have made a decision that a warrantless arrest is lawful to justify that the situation falls under specific categories.

They will also have to show that they had reasons to believe that probable cause is met.

Any documentation may help in showing what an officer intended when he decided to perform an action and what facts supported belief that a search was lawful. This principle especially applies to warrantless searches: They are unreasonable if they are not supported by probable cause.

The Role of the Courts One must consider whether a warrant can always be obtained before making an arrest. It may sometimes be necessary to take a person into custody immediately.

In order to clarify any misunderstandings, it is important to emphasize that the issue raised by the litigation in Southern California is not whether an arrest can sometimes be justified without a warrant.

One has to look at whether the conditions of the likelihood of escape actually apply to any government action, not just a warrantless arrest. It may seem at odds with any constitutional right if the government has the absolute power to arrest anyone anywhere without a warrant.

The Fourth Amendment does apply to the immigration authority of the US government, even though it does not apply to all government conduct. The government also has to show that taking a person into custody is reasonable.

The Broader Constitutional Principle

The scope of Fourth Amendment, however, goes beyond the authority of immigration officers. A law that authorizes a warrantless search may be considered to provide the same protection as probable cause. A government official may take a person into custody without a warrant under certain conditions provided by a law. A court may review if those who believe that they can take a person into custody are in the right. It will have to analyze if the government was justified in its intentions and that government conduct was justified.

The current litigation in southern California gives an example of one of the issues in law enforcement involving warrantless arrests. There are times when taking a person into custody does not violate the Fourth Amendment.

Although a warrantless search cannot be totally lawful, sometimes it is justified if one reviews the factors that show whether the circumstances fall under its provisions. However, there are other factors beyond the Fourth Amendment that apply to warrantless searches conducted by immigration officers.

The government needs to show that a search will produce results that support its objectives. This is why the government has the most authority to conduct searches along international borders. In turn, its authority over warrantless searches conducted within the country’s interior is limited.

It has already been mentioned that when it comes to searches, a warrant is not always required.

One must distinguish between a warrantless search and a warrantless arrest. This distinction becomes significant when analyzing a case involving warrantless arrests of people who have violated immigration laws.

The government must show that there is probable cause that such a person would evade its custody before it can take them into custody.

Why It Matters

The distinction between a warrantless arrest and a warrantless search matters because government authority is not unlimited. Immigration officers may have significant enforcement powers, but those powers remain subject to constitutional and statutory requirements.

The Southern California litigation illustrates why those requirements matter in practice. A warrantless arrest can affect a person's freedom immediately, making the legal basis for that arrest important to both the government and the individual.

Conclusion The government may have authority to make a warrantless arrest under certain circumstances. However, that authority depends on the requirements established by the Constitution and federal immigration law.

The Southern California litigation demonstrates that the question is not simply whether a warrant was obtained. The circumstances surrounding the arrest, including the likelihood of escape and the facts supporting probable cause, can determine whether the government's action complies with the law.

1. M.B. v. Noem, No. 2:25-cv-05656 (C.D. Cal. Sept. 2, 2026).

2. U.S. Const. amend. IV.

3. United States v. Watson, 423 U.S. 411, 417–24 (1976). A warrantless public arrest made on probable cause is not per se unreasonable under the Fourth Amendment to the Constitution.

4. 8 U.S.C. § 1357(a)(2).

5. Almeida-Sanchez v. United States, 413 U.S. 266, 273–75 (1973). The warrantless search by agents of the Border Patrol away from the border conducted without probable cause or consent violated the Fourth Amendment.

6. Gerstein v. Pugh, 420 U.S. 103, 111–14 (1975). The Supreme Court used the term probable cause for the quantum of information necessary to satisfy the Fourth Amendment’s particularity requirement for a significant pretrial detention.

7. 8 U.S.C. § 1357(a)(2); 8 C.F.R. § 287.3.

8. See Arizona v. United States, 567 U.S. 387, 394–410 (2012), discussing federal preemption of state laws pertaining to immigration and the immigration control policy of the federal government.