Immigration enforcement in the United States is generally a civil matter, handled exclusively by federal agents working for U.S. Immigration and Customs Enforcement (ICE) or Customs and Border Patrol. State and local law enforcement personnel, including deputy sheriffs, do not have authority to arrest or detain individuals solely for civil infractions—such as being undocumented or overstaying a visa—unless they are expressly authorized through a valid 287(g) agreement.