Internet Service Providers (ISP's) are companies that provides people with access to the internet.  With respect to individual users, an Internet Service Provider will assign a string of numbers to a customer's modem.  This string of numbers is known as an "Internet Protocol."  Consequently, when users communicate and share information online or access websites, the Internet protocol addresses of the parties is recorded.  Moreover, individuals must provide their subscriber information to Internet Service Providers in order to acquire their service. Recently, the Arizona Supreme Court ruled that police do not need a search warrant to obtain a person's Internet Protocol address or specific subscriber information.

The United States Constitution guarantees people the right to be secure in the "persons, houses, papers and effects" against unreasonable searches and seizures.  As technology develops, the 4th Amendment protections have extended to the contents of people's cell phones, tracking devices on vehicles, etc.  Moreover, police can generally search a protected area only when their given consent by the owner or after they've acquired a warrant signed by a judge which is supported by probable cause.

The 4th Amendment applies and limits law enforcement's ability to search places where people have a "legitimate expectation of privacy."  For example, this might include a person's home, office, vehicle, etc.  However, it would not extend to property which is abandoned, thrown away as garbage or where a persons disavows an ownership interest.

In the case of Internet  Protocol (IP address) or Subscriber Information (Names, Home Address), the Arizona Supreme Court determined there is no legitimate expectation of privacy because people who access the internet, exchange information and download data from websites voluntarily provide their personal information to third party Internet Service Providers.  Consequently, once users are their information public by accessing the internet, any expectation of privacy is forfeited.  As a result, police need only to serve a subpoena on an Internet Service Provider to obtain information concerning an IP address, where the user is located and the user's identity.

Although this case concerned a police investigation related to child pornography, it could affect anyone using the internet for activities which are suspected of being illegal.  For example, people selling items suspected of being stolen, advertising marijuana or other drugs for sale online or engaging in internet gambling could find themselves at risk of arrest and prosecution based on law enforcement's discovery of internet subscriber information.