This is something we have to watch very, VERY closely!
One of the most basic – and important – hallmarks of American democracy is that the United States military cannot, except under very narrow exceptions, be deployed on our own soil. There are excellent reasons for this, the number one being that turning the military on its own people is what autocrats and dictators do to suppress dissent, empower corruption, and violate civil liberties in egregious ways.
Under the power of the U.S. Constitution, the president is the Commander-in-Chief of America’s armed forces, but the U.S. Congress is the branch of government in control of the military’s domestic activities (thank God once again for the separation of powers!).
In 1878, Congress passed the Posse Comitatus Act (PCA), which prevents members of the federal armed forces from participating in civilian law enforcement activities unless they have been “expressly authorized” by Congress. However, there are two exceptions to this: the Insurrection Act and the president’s authority over the National Guard.
Insurrection Act
The Insurrection Act authorizes the U.S. president to use the military domestically to suppress “any insurrection, domestic violence, unlawful combination, or conspiracy.” These terms are not defined in the statute, unfortunately, which leaves them far too ambiguous – and open to far too broad interpretations.
In the 1827 U.S. Supreme Court case Martin v. Mott, the Court held that the president alone decides when to invoke the Insurrection Act because he is “presumed to act in obedience to his duty.” Because the president is the final decision on whether an emergency has arisen domestically, Congress is given no formal role in this process and there are no time restrictions on the deployments.
The National Guard
The National Guard is the only branch of the U.S. military that has both state and federal responsibilities. Therefore, the Guard can be controlled by either state or federal leaders, depending upon their deployment status. In the District of Columbia, the National Guard is always under the command and control of the president. Therefore, the president can deploy the D.C. Guard for law enforcement purposes anytime.
The National Guard has three deployment types:
State Active Duty (SAD) status: The National Guard carries out state-defined missions at the state’s expense and serves under the command and control of the state or territory’s chief executive. With SAD, governors are given broad authority to use the Guard forces as they see fit, and they are generally used in the case of emergencies and civil disturbances
Title 32 (i.e., “hybrid”) status: This status is generally used for training exercises. Examples of Title 32 being used in non-training activities include post-9/11 airport security, conducting relief operations after Hurricane Katrina, and providing support to U.S. Customs and Border Protection at the U.S.-Mexico border.
Title 10 status: Under Title 10 status, National Guard units are called into federal service, or “federalized,” by the U.S. president and placed under federal command and control just as if the Guard personnel were members of the regular armed forces. As such, federalized National Guard personnel are governed by the Posse Comitatus Act.
In April 2018, Defense Secretary James Mattis authorized up to 4,000 National Guard troops to deploy to the U.S. border with Mexico to support the Department of Homeland Security’s border security mission there.