Bill of Rights · 4th Amendment
Fourth Amendment
Ratified December 15, 1791
Verbatim
Exact text as ratified.
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.
Plain English
A translation that drops archaic words but keeps the meaning, including the parts courts still argue about.
You have the right to be secure in your body, your home, your belongings, and your communications, and the government cannot search or take them unreasonably. The government cannot get a warrant unless it has good reason to believe a crime is involved, swears to that reason under oath, and describes specifically what will be searched and what will be taken.
What this means for you
The government, including police, cannot search you, your phone, your car, your home, your bag, or your mail without one of three things: a warrant, your consent, or a recognized legal exception. Most everyday encounters with police involve consent. If a police officer asks "can I search your bag?" and you say yes, the search is legal. If you say no, they need a warrant or an exception.
You have the right to refuse consent. Refusing consent is not evidence of guilt and cannot legally be used against you. You can say "I do not consent to this search" calmly and clearly, and the officer cannot punish you for it. They may search anyway, claiming an exception, but that becomes a question for a court later, not for you in the moment. Your job is to clearly state that you do not consent.
Phones get special protection. Since Riley v. California (2014), police cannot search your phone without a warrant, even if they have arrested you. They can ask for your passcode; you do not have to give it.
Schools have different rules. School officials can search students with a lower standard than police use. They need "reasonable suspicion," not probable cause. This applies to lockers, backpacks, and sometimes phones, depending on your state.
Cars have different rules too. Police can search a car if they have probable cause to believe it contains evidence of a crime, without a warrant. They can ask to search anyway; you can refuse.
About
The Fourth Amendment was ratified in 1791 and originally restricted only the federal government. Through the Fourteenth Amendment, it now restricts every level of government: federal, state, county, and city.
The amendment uses the word "papers," which in 1791 meant private letters, journals, and documents. Modern courts have extended this protection to phone contents, emails, text messages, location data, and other digital records. Two cases shaped this: Riley v. California (2014) ruled that police need a warrant to search a phone, even after an arrest. Carpenter v. United States (2018) ruled that police generally need a warrant to access cell phone location data. The plain-English version above renders "papers" as "communications" because that is what the modern legal protection covers.
The word "unreasonable" is doing a lot of work in the amendment. Courts have spent over two centuries defining what makes a search reasonable: what counts as probable cause, what exceptions to the warrant requirement exist, what consent means, what the rules are at borders, in cars, in schools, and in workplaces. New cases continue to reach the Supreme Court every year. The protection in the text is broad; the protection in practice depends heavily on what courts are currently saying.