The Third Party Doctrine is a legal principle in United States law stating that individuals have no reasonable expectation of privacy for information voluntarily shared with third parties, such as banks, phone companies, or internet service providers. This means that law enforcement agencies can often access such data without a warrant, as it is considered to be held by someone other than the individual. The doctrine originated from Supreme Court cases in the 1970s and has significant implications for digital privacy, especially as more personal information is stored and transmitted through third-party services. Critics argue it is outdated in the age of cloud computing and mass data storage.