The U.S. military has long been banned from performing police functions within the United States. But a new Department of Defense publication says there are exceptions to the Posse Comitatus Act (PCA) of 1878, which drew the line at the armed forces performing civilian law enforcement activities, like arresting people, spying on them, and searching their homes.

The publication states that there “are several forms of direct assistance to civilian law enforcement by military personnel that are permitted under the Military Purpose Doctrine. The Military Purpose Doctrine provides that law enforcement actions that are performed primarily for a military purpose, even when incidentally assisting civil authorities, will not violate the PCA.”

Authorized forms of assistance include, but are not limited to, investigations related to the Uniform Code of Military Justice, enforcement actions on a military installation, and measures to protect classified military information or equipment, according to Steven Aftergood at Secrecy News.

Aftergood discovered that within the document, the military added a new, key term as it applies to military actions within the country: “complex catastrophe.”

A complex catastrophe is defined as: “Any natural or man-made incident, including cyberspace attack, power grid failure, and terrorism, which results in cascading failures of multiple, interdependent, critical, life-sustaining infrastructure sectors and causes extraordinary levels of mass casualties, damage or disruption severely affecting the population, environment, economy, public health, national morale, response efforts, and/or government functions.”

It is important to note this new term, Aftergood wrote, because it can be used to “magnify requirements for defense support of civil authorities”—in other words, make it okay for the military to take action at home.

-Noel Brinkerhoff

To Learn More:

When Can the Military Support Civil Authorities? (by Steven Aftergood, Secrecy News)

Defense Support of Civil Authorities (Department of Defense) (pdf)

New Rule Allows U.S. Military to Act without President’s Authorization (by Matt Bewig, AllGov)

Is the Government Breaking the Posse Comitatus Law? (by Noel Brinkerhoff, AllGov)