Footnote 73 of the FFIEC Examination Manual (2010) gives a good "starter" list of law enforcement agencies.
Examples of agencies to which a SAR or the information contained therein could be provided include: the criminal investigative services of the armed forces; the Bureau of Alcohol, Tobacco, and Firearms; an attorney general, district attorney, or state’s attorney at the state or local level; the Drug Enforcement Administration; the Federal Bureau of Investigation; the Internal Revenue Service or tax enforcement agencies at the state level; the Office of Foreign Assets Control; a state or local police department; a United States Attorney’s Office; Immigration and Customs Enforcement; the U.S. Postal Inspection Service; and the U.S. Secret Service. For additional information, refer to Bank Secrecy Act Advisory Group, “Section 5—Issues and Guidance,†The SAR Activity Review—Trends, Tips & Issues, Issue 9, October 2005, page 44 at www.fincen.gov.My practical test would be if they can arrest someone; i.e. they have police powers, then they are law enforcement. Otherwise they are not. The role of a state's "adult protective services" department varies from one state to the next.
The answer is specific to your state. Daisy offers a good example, but it would
not be true in my home state.