Under the Fourth Amendment , law enforcement officers must receive written permission from a court of law , or otherwise qualified magistrate , to lawfully search and seize evidence while investigating criminal activity . Following the September 11 attacks , the 2001 Patriot Act gave law enforcement officers permission to search a home or business without the owner 's or the occupant 's consent or knowledge , amongst other provisions , if terrorist activities were suspected . The Act was criticized for its perceived violation of civil liberties and has generated a great deal of controversy since its enactment . In '' United States v. Antoine Jones '' , the court found that increased monitoring of suspects caused by the Patriot Act directly put the suspects ' constitutional rights in jeopardy . For a time , the Act allowed for agents to undertake " sneak and peek " searches . Critics such as the ACLU strongly criticized the law for violating the Fourth Amendment
September 11 attacks
September 11 attacks
Militarization of police