Border Fiction Made Real: How Search and Seizure Laws Degrade on the 100-Mile Border Zone

Learn more about Hillary Mushkin's "Three Border Ecologies" in this video with additional footage by Meena Nanji and Stacie Jaye Meyer.

In Havre, Montana, a town located 35 miles south of the US-Canadian border, a U.S. Citizenship and Border Protection (CBP) officer questioned Ada Suda and Mimi Hernandez, both native-born citizens, about their immigration status. Hearing the women speaking Spanish as they waited in the checkout line at a convenience store, the CBP officer asked both for their IDs and questioned them in a tense exchange that lasted nearly 40 minutes.  Nine months later, on February 2019, the ACLU filed a lawsuit on the women’s behalf, arguing that the officer had violated their constitutional rights against racial discrimination and unreasonable searches and seizures. The incident drew national attention because it exemplified a longstanding pattern of abuse committed by CBP in a region known as the 100-mile zone. 

Created by policymakers in the 1940s, the border zone extends 100 miles inland from the nation’s land and sea boundaries and houses nearly two-thirds of the U.S. population. Within this jurisdiction, CBP possesses a broad authority to conduct immigration checks by questioning individuals and searching property without warrant.  Critics have long claimed that CBP officers push the limits of their sweeping authority inside the zone by engaging in racial profiling and unlawful stops, searches and detentions.  Meanwhile, CBP has often defended its operations in this region as an integral component of its mandate to “secure the U.S. border” and cites the Supreme Court cases that have upheld the constitutionality of its traffic checkpoints.

This map uses dot density mapping to illustrate the population density of areas within 100 nautical miles (~115 miles) of the U.S. border or international water body. | Courtesy of ESRI

A recent study of the Immigration and Naturalization Service (INS) sheds new insight into this debate by raising questions about the very legitimacy of the 100-mile zone.  While today’s CBP expresses much confidence about the lawfulness of its enforcement strategies, this was not always the case.  In the 1940s, Border Patrol leaders admitted that their officers “[stopped] vehicles promiscuously on the highways leading away from the border … without proper authority.”  In order to address this problem, the INS lobbied Congress to pass legislation that shored up the tenuous legal status of its immigration checks and protected INS employees, including the Border Patrol, from lawsuits. The 100-mile zone was the chief byproduct of this effort to legalize practices that the INS had long recognized as illegal.


Border Patrol badge | Jonahtan McIntosh / Flickr / CC BY 2.0
Border Patrol badge | Jonahtan McIntosh / Flickr / CC BY 2.0

Shortly after the creation of the Border Patrol in 1924, immigration officials began to question the legality of the unit’s operations beyond the U.S.-Mexico border.  While they possessed the clear legal authority to make arrests and conduct searches and seizures without warrant at the international boundaries, they were uncertain about the reach of that authority beyond the line.  The sparsely worded statute regarding the Border Patrol failed to illuminate the issue, and the immigration laws were just as vague on this point.

By 1933, these ambiguities led Commissioner General William MacCormack to observe that the agency often conducted apprehensions “without due regard for our constitutional procedure and that there is, in many of the cases, distinct lawlessness.” As part of his broader effort to reform the INS and protect agency employees from liability, MacCormack ordered the Border Patrol to end its practice of arresting immigrants without warrant (except in certain cases) and its vehicular stops beyond the border. 

Border Patrol officials in the Southwest railed against the new orders, arguing that they flew in the face of practices exercised since the unit’s founding in 1924. They griped that the warrantless detention and “rigid questioning” of undocumented immigrants were necessary to extract from them the evidence essential for a warrant.

In the 1930s, local Border Patrol officials paid lip service to the prohibition on warrantless arrests.  But by the 1940s, MacCormack’s reforms gave way in the face of the unprecedented logistical demands of the Bracero Program. Initially conceived as an emergency guest worker program that would only last the duration of the War, it, at the urging of southwestern agribusiness, lasted for 22 years and employed 4.5 million Mexican nationals. The program also provided the stimulus for the undocumented entry of another 5 million Mexican workers.  Lacking the money and manpower to manage the sheer volume of new arrivals, local Border Patrol officials took steps to enhance their enforcement capacities.

Key to this campaign was Grover C. Wilmoth, the El Paso Immigration and Naturalization District Director, who in 1941, began pursuing legislative amendments on behalf of the Border Patrol. For several years, Wilmoth worked with the attorney general’s office to plan and draft what would become Public Law 613, the first revision of the Border Patrol statute since 1925.  While the measure was the subject of little debate in Congress, the INS correspondence files document the extensive role played by southwestern agency officials in shaping the law.

Cleghorn Wilderness site, a vast wild area where undue search and seizure could potentially happen because it is within the 100-mile border zone | Jena Lee
Cleghorn Wilderness site, a vast wild area where undue search and seizure could potentially happen because it is within the 100-mile border zone. The site was part of Hillary Mushkin's "Three Border Ecologies" project. | Jena Lee

Through legislative reform, Wilmoth aimed to reverse the changes instituted by MacCormack in the 1930s.  Indeed, by the 1940s, southwestern INS officials openly criticized MacCormack’s attempt to make the Border Patrol follow the letter of the law.  The warrant requirement was a particular focus of their attacks; since it cut Border Patrol apprehensions in half, local INS leaders argued that it reduced the effectiveness of the agency as a whole.  At the same time, Wilmoth fought for legislative amendments that would allow the Border Patrol to skirt the Fourth Amendment — specifically, its prohibitions against warrantless arrests and unreasonable searches and seizures — on private property and the nation’s highways.

Wilmoth wanted the latter not only to augment the legal authority of his agents but also to provide legal cover for what he and other Border Patrol officials openly characterized as dubious legal practices. In the early 1940s, southwestern immigration officials admitted that despite the reasonable cause standards enumerated by the Border Patrol statute for car stops, since 1924, Patrol officers had stopped vehicles with little or no cause or suspicion in an area 100 miles north of the border.  They further disclosed that they continued the practice even in the face of “innumerable” questions regarding its legality. Wilmoth and the Border Patrol could have chosen to train officers to abide by reasonable cause standards, but they didn’t. Instead, they sought a legislative amendment to legitimize standing procedures, despite their questionable legality.

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Southwestern INS officials took comfort in the fact that Public Law 613 restored the former status quo.  It terminated the reforms of the 1930s and sanctioned practices that agency officials themselves once characterized as lawless. The new statute specifically authorized immigration officials to engage in the warrantless arrest of undocumented immigrants beyond the border. It also freed Border Patrol officers from determining probable cause or reasonable suspicion prior to a car stop.  Instead, they were given broad authority to conduct stops and searches within a “reasonable distance from any external boundary of the United States.” By the following year, INS officials used their administrative discretion to define this reasonable distance to be 100 air miles from the border. 

Yet, this definition was negotiable rather than fixed.  If southwestern immigration officials could establish the existence of “unusual circumstances” in their districts, INS leaders in Washington, DC would authorize the extension of the reasonable distance rule beyond 100 air miles.  As a result, cities such as Austin, San Antonio, Phoenix, and Albuquerque, among others, were declared to fall within a reasonable distance of the US-Mexico border.

Wilmoth had hoped that Public Law 613 would include language that secured the Border Patrol’s ability to conduct warrantless searches of private property, particularly the farms and ranches next to the international boundary. But he withdrew this proposal due to concerns that it would trigger the opposition of southwestern farmers who, in turn, would block the passage of the measure in its entirety. 

The INS continued to lobby for the amendment, and by 1951, it achieved the passage of a federal law, authorizing immigration officials to search private land (but not dwellings) without warrant in a 25-mile zone adjacent to the border and nested within the 100-mile zone.


Congressional legislators recently proposed bills that would retrench the 100-mile border zone. If passed, the measures would shrink the 100-mile zone to 25 miles and the 25-mile zone to 10 miles. Yet, due to a lack of support, it’s very likely that the measure will not pass. Any transformation of the border zone faces an uphill battle because many now take it for granted, accepting its existence as the law of the land.  But this view of the 100-mile zone fails to consider its troubling origins.  Its creation was not informed by the will of the people or a commitment to constitutional principles and the rule of law.  Instead, the 100-mile border zone was the invention of Border Patrol officers who made sure that practices they had long recognized as illegal became law. 

Top Image: View of San Clemente Border Patrol station | Lena Martinez-Miller


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