Some amendment rulings consider things not taken into account at the time they were written, but I would think they were well aware of border checkpoints at the time even, and the idea for internal checkpoints. Was something mentioned about this at the time? Did what constitute 'unreasonable' change? Seems at the time especially, the 100 mile range would have made the amendment fairly limited.

People might not see this outside the southern border much, but in the southwest, getting searched is totally common (same as the the border), just for going from one town to the next, in literally any direction for some places.

  • Results are asked about here law.stackexchange.com/questions/95821/…
    – user52272
    Sep 28, 2023 at 17:16
  • "Was something mentioned about this at the time?" At what time? Which ruling are you asking about? If you're asking about the ruling that declared the checkpoints to be constitutional, of course they were aware of checkpoints at the time, because that's what the case was about. Or are you asking about when the fourth amendment was passed? There was no awareness of checkpoints then because immigration law basically didn't exist yet. But anyway getting stopped isn't the same as getting searched, and probable cause is needed for a search.
    – phoog
    Sep 28, 2023 at 22:43
  • When the 4th amendment was passed.
    – user52272
    Sep 28, 2023 at 22:50
  • 1
    Internal immigration checkpoints began roughly a century and a half after the fourth amendment was passed and are concerned with enforcing laws that similarly did not exist until over a century after it was passed. There was basically no such thing as illegal aliens in 1789.
    – phoog
    Sep 28, 2023 at 23:26

2 Answers 2


The constitutionality of warrantless internal border checkpoints conducting searches without probable cause, within 100 miles of the U.S. border, has been upheld by the courts in the face of challenges to this practice rooted in the 4th Amendment protections against search and seizure.

Essentially, the line of reasoning is that warrantless searches at a border crossing are allowed as a way to secure U.S. borders for enforcement of customs and immigration laws (in line with universal historic practice in common law countries as of 1791 when the 4th Amendment was adopted), and that these searches don't have to be precisely on the international boundary line. Within that framework, a bright line of 100 miles from the border has been upheld as a reasonable exercise of discretion by the federal government concerning how far from the international boundary line is too far. Courts have so far not accepted any constitutionally mandated limited principle to restrain this 100 mile rule even though it pushes the boundaries of reasonableness.

The history of the rule and the U.S. Supreme Court part of the relevant case law is discussed at length here (links to the cases cited bvelow are available at this link):

In 1946, Congress quietly passed a statute giving U.S. Customs and Border Protection the authority to stop and search all vehicles within a “reasonable distance” from the border. Shortly thereafter, the agency defined that distance as 100 miles from all land borders and coastlines, thus crowning themselves kings of what is now known as the “100-mile zone,” an area in which nearly two-thirds of the U.S. population lives. That regulation, which effectively allows border officers to disregard key Fourth Amendment protections within that area, has remained in place ever since.

(The ACLU clarifies that the regulations implementing the 1946 statute adopted by Congress were adopted in 1953.)

The linked discussion of the legal history of the rule continues as follows:

In 1973, a divided 5-4 Court planted the first landmine for the demolition of the Fourth Amendment in Almeida-Sanchez v. United States. The case, at first blush, sounds good: In it, the Court held that immigration officers searching a car for undocumented people without a warrant or probable cause was unconstitutional. But in a concurrence, Justice Lewis Powell suggested treating the areas around the border differently from the rest of the country. Searches near the border, he wrote, “draw a large measure of justification from the Government’s extraordinary responsibilities and powers with respect to the border.” Thus, he suggested that something analogous to an “area warrant,” which judges issue to city officials to conduct housing code inspections in residential areas, could suspend the need for individualized probable cause within the 100-mile zone.

Powell was also sympathetic to the government’s arguments that deportation is a civil proceeding, and that few migrants faced criminal prosecution for crossing the border without authorization. Because border stops were unlikely to lead to criminal prosecutions, he wrote, border searches are not like “random area searches which are no more than ‘fishing expeditions’ for evidence to support prosecutions.” . . .

Just two years after Almeida-Sanchez, the justices who had dissented from that opinion had apparently shed their reservations about shredding the meaning of the Fourth Amendment at the border. In a unanimous decision in United States v. Brignoni-Ponce, the Court lowered the standard for border officers conducting “roving patrols,” where they stop drivers on highways within the 100-mile zone to inquire about citizenship status, to the lowest standard: reasonable suspicion. The justices also explicitly stated that race could a factor when determining the “reasonableness” of an officer’s suspicion, functionally sanctioning the racial profiling practices of border agents in the process.

Then, in 1976, the Court in United States v. Martinez-Fuente upheld military-style checkpoints at which agents, again, randomly stop cars to question people about their immigration status. According to the justices, whose personal experiences passing through Border Patrol checkpoints were presumably limited, these encounters aren’t as intrusive as traditional law enforcement stops and thus didn’t require “individualized suspicion” at all. In dissent, Justice William Brennan, joined by Justice Thurgood Marshall, called the decision an “evisceration” of Fourth Amendment protections.

The Supreme Court has even extended the leeway that it grants border officers to run-of-the-mill cops in states like Arizona and Texas. In 2012, the Court in Arizona v. United States partially upheld SB1070, an Arizona law that deputized local law enforcement to enforce federal immigration law by allowing them to ask about the immigration status of any detained person they suspect is undocumented. In doing so, the Court enabled state law enforcement cops to engage same racial profiling that has become routine amongst immigration officers.

Organizations like the ACLU have sought to challenge this great distance from the actual international boundary line as excessive and continue to pursue both legal challenges and legislative reforms to narrow this rule, on the theory that it is being abused to perform searches that should not come within the border checkpoint exception to the requirement of probable cause to conduct searches and seizures. But so far, these challenges have been unsuccessful. (The ACLU has also argued with somewhat more success in particular cases, that the Border Patrol overstates its authority under the case law, statues, and regulations above, in the 100 mile zone.)

On the other hand, keep in mind that internal checkpoint search authority is not granted to all law enforcement officers. It is limited to federal customs and immigration law enforcement agents, and to other federal, state, and local law enforcement agents deputized by federal law enforcement agents to carry out searches for those purposes.

  • "and that these searches don't have to be precisely on the international boundary line": this implies that officers at an internal checkpoint have the same search authority as they do at a port of entry. They do not. In fact, they cannot search vehicles (beyond what is in plain sight) without probable cause, consent, or a warrant.
    – phoog
    Sep 28, 2023 at 22:20
  • @phoog they definitely search vehicles, including running a dog through, whatever, without probable cause, consent, or a warrant. Just like being at the real border.
    – user52272
    Sep 28, 2023 at 23:16
  • @user14094230 they use the dog to claim probable cause. Thats not the same as searching without probable cause. I've had a vehicle searched at the real border, have you? There was no dog, no suspicion of a crime, no request for consent. At a checkpoint they need one of these things before they can open the trunk or glove compartment, etc. Details are given in the ACLU link in this answer.
    – phoog
    Sep 28, 2023 at 23:29
  • Ask anyone who's spend time along the border, they'll at least know someone who has been searched.
    – user52272
    Sep 28, 2023 at 23:31
  • @user14094230 sure. But my point is that they do this with probable cause or with consent. If they say "do you mind if I look in your trunk" and you acquiesce then the search is legal because you consented to it. If they bring the dog and the dog alerts then they have probable cause. If they claim falsely that the dog alerted then the search is illegal. At the real border they just say "I'm going to search your stuff now." It's an entirely different legal context.
    – phoog
    Sep 28, 2023 at 23:41

I would think they were well aware of border checkpoints at the time even, and the idea for internal checkpoints.

Well surely there were border checkpoints in the eighteenth century, but not internal checkpoints as we know them today. They were not formalized until roughly a century and a half after the bill of rights.

But the fourth amendment doesn't actually prohibit searches without warrant:

The right of the People to be secure in their persons, houses, papers and effects, against unreasonable searches and seizures, shall not be violated, and no warrants shall issue, but upon probable cause supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.

The text provides some requirements that valid warrants should meet, but it does not exclude the possibility that some searches could be "reasonable" in the absence of a warrant.

The supreme court has found that warrantless searches of people entering the country at a port of entry are reasonable even without probable cause because of a long history of such searches. By contrast, the court has found that a warrantless search at an internal checkpoint must be justified by probable cause or consent. In US v. Ortiz the court held

that, at traffic checkpoints removed from the border and its functional equivalents, officers may not search private vehicles without consent or probable cause.

Immigration officers have greater powers within 100 miles of the border; notably they can set up checkpoints to investigate the immigration status of passing motorists. There is a good deal of concern that officers' conduct at these checkpoints goes beyond the court's intention in Martinez Fuerte and that they abuse the requirement to have probable cause, but the very abuse of that requirement shows that they do not claim the power to search vehicles without probable cause or consent.

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