Now you’ve got me curious, so I checked Wikipedia. I didn’t realize that Coast Guard was exempted for the original act.
Here are the current exceptions to the Posse C. Act per
Wikipedia:
Exclusions and limitations[edit]
There are a number of situations in which the Act does not apply. These include:
Army and Air National Guard units and state defense forces while under the authority of the governor of a state;
Federal military personnel used in accordance to the Insurrection Act, as was the case during the 1992 Los Angeles riots.
Under 18 U.S.C. § 831, the Attorney General may request that the Secretary of Defense provide emergency assistance if domestic law enforcement is inadequate to address certain types of threats involving the release of nuclear materials, such as potential use of a nuclear or radiological weapon.
Such assistance may be by any personnel under the authority of the Department of Defense, provided such assistance does not adversely affect U.S. military preparedness. The only exemption is nuclear materials.
Support roles under the Joint Special Operations Command
Exclusion applicable to U.S. Coast Guard[edit]
See the Law Enforcement Detachments and Missions of the United States Coast Guard for more information on U.S. Coast Guard law enforcement activities.
Although it is an armed service,[12] the U.S. Coast Guard, which operates under the Department of Homeland Security, is not restricted by the Posse Comitatus Act.
The Coast Guard enforces federal laws within its jurisdiction, even when operating as a service within the U.S. Navy.[5]
In December 1981, additional laws were enacted clarifying permissible military assistance to domestic law enforcement agencies and the Coast Guard, especially in combating drug smuggling into the United States.
Posse Comitatus clarifications emphasize supportive and technical assistance (e.g., use of facilities, vessels, and aircraft, as well as intelligence support, technological aid, and surveillance) while generally prohibiting direct participation of Department of Defense personnel in law enforcement (e.g., search, seizure, and arrests).
For example, a U.S. Navy vessel may be used to track, follow, and stop a vessel suspected of drug smuggling, but Coast Guard Law Enforcement Detachments (LEDETs) embarked aboard the Navy vessel would perform the actual boarding and, if needed, arrest the suspect vessel’s crew.[5]
Thanks for posting these regulations re the Coast Guard:
Posse Comitatus clarifications emphasize supportive and technical assistance (e.g., use of facilities, vessels, and aircraft, as well as intelligence support, technological aid, and surveillance) while generally prohibiting direct participation of Department of Defense personnel in law enforcement (e.g., search, seizure, and arrests).
For example, a U.S. Navy vessel may be used to track, follow, and stop a vessel suspected of drug smuggling, but Coast Guard Law Enforcement Detachments (LEDETs) embarked aboard the Navy vessel would perform the actual boarding and, if needed, arrest the suspect vessel’s crew.[5]