Can U.S. border guards do warrantless searches?
<p>If I am a U.S. citizen entering the United States by car from Canada or Mexico can border guards legally search my car without a warrant?</p>

<p>Yes. At international borders and international airports (because those are the equivalent of a border), US customs officers may do searches of people and belongings without a warrant and without any particular reason to think they'll find contraband. This includes the authority to do some level of disassembly of the car, if they then reassemble it. See <em>United States v. Flores-Montano</em>, <a href="https://www.law.cornell.edu/supct/html/02-1794.ZO.html" rel="nofollow">541 U.S. 149</a>. This is known as the "border search exception." </p>

<p>Moreover, police <em>normally</em> don't need warrants to search your car if it was mobile when they found it and if they have probable cause to believe they'll find contraband. This is known as the "automobile exception" or the "motor vehicle exception." It was established in <em>Carroll v. US</em>, <a href="https://supreme.justia.com/cases/federal/us/267/132/case.html" rel="nofollow">267 U.S. 132</a>. Individual states may have stricter requirements on police searches, but the Fourth Amendment doesn't require police to get a warrant to search your car if, say, you drove it up to a checkpoint and they have probable cause. The difference at a border is that they don't need probable cause and the car never had to be mobile: they can search you on a hunch.</p>

<blockquote>
  <p>Border searches [are] not subject to the warrant provisions of the
  Fourth Amendment and [are] "<strong>reasonable</strong>" within the meaning of that
  Amendment.</p>
</blockquote>

<p><a href="https://scholar.google.com/scholar_case?case=6107136132398268257" rel="nofollow">United States v. Ramsey, 431 US 606 (1977)</a></p>

<p>The fourth amendment only denounces <strong>unreasonable</strong> searches.</p>

<blockquote>
  <p>Border searches, then, from before the adoption of the Fourth
  Amendment, have been considered to be "reasonable" by the single fact
  that the person or item in question had entered into our country from
  outside. There has never been any additional requirement that the
  reasonableness of a border search depended on the existence of
  probable cause. This longstanding recognition that searches at our
  borders without probable cause and without a warrant are nonetheless
  "reasonable" has a history as old as the Fourth Amendment itself.</p>
</blockquote>

<p>The <em>Ramsey</em> case is full of good stuff, like this:</p>

<blockquote>
  <p>"But a port of entry is not a traveler's home. His right to be let
  alone neither prevents the search of his luggage nor the seizure of
  unprotected, but illegal, materials when his possession of them is
  discovered during such a search. Customs officials characteristically
  inspect luggage and their power to do so is not questioned in this
  case; it is an old practice and is intimately associated with
  excluding illegal articles from the country."</p>
</blockquote>

<p>quoting <em>United States v. Thirty-seven Photographs</em>, 402 U. S. 363, 376 (1971)</p>

united-states search-and-seizure