United States Postal Inspection Service

The United States Postal Inspection Service (USPIS), or the Postal Inspectors, is the federal law enforcement arm of the United States Postal Service. It supports and protects the U.S. Postal Service, its employees, infrastructure, and customers by enforcing the laws that defend the United States' mail system from illegal or dangerous use. Its jurisdiction covers any crimes that may adversely affect or fraudulently use the U.S. Mail, the postal system, or postal employees. With roots going back to the late 18th century, the USPIS is the country's oldest continuously operating federal law enforcement agency.

There are approximately 200 federal crimes that can be committed which involve the mail. Therefore, the U.S. Postal Inspection Service's activities are broad and ever-changing. In 2021, postal inspectors made 5,141 arrests leading to more than 3,700 convictions, mostly involving mail theft, mail fraud, and prohibited mailings. The growth in illegal narcotics has resulted in over 19,000 arrests and the seizure of $18 million in drug proceeds since 2010. In 2022, Postal inspectors performed over 5,300 seizures that resulted in almost 17,000 pounds of illicit drugs being taken off the streets. In some cases, these seizures were performed with the assistance of a detection dog.

As of 2022, there were about 1,250 postal inspectors, who are authorized to carry weapons, make arrests, execute federal search warrants, and serve subpoenas.