Could Trump legally deploy the military to deport illegal migrants? It’s possible.

Critics of President-elect Trump’s proposal to involve the military in deporting undocumented immigrants argue that it may violate the Posse Comitatus Act of 1878. However, this interpretation is not definitive and may not apply in this situation.

The Posse Comitatus Act, established in 1878, restricts the use of federal military troops for law enforcement purposes unless explicitly authorized by the Constitution or Congress. While some courts have ruled against the use of military in law enforcement, the Supreme Court has not definitively concluded on this matter.

There are concerns regarding the origins and intent of the Posse Comitatus Act, which was initially driven by Southern resentment following the Civil War over the deployment of federal troops to protect freed slaves. Congress did not design the act to limit the president’s authority to utilize the military, but rather to counteract the Cushing Doctrine that allowed unelected civilian officials to command military forces.

Despite some court interpretations, Congress has explicitly permitted military involvement in civilian law enforcement during emergencies through acts like the Insurrection Act of 1807. Presidents have utilized these powers in the past, including President Grover Cleveland using the Insurrection Act to protect Chinese miners during riots.

While the use of military force for mass deportation may be considered novel, the ongoing immigration crisis may warrant invoking the Insurrection Act. If the administration can demonstrate that criminal cartel-driven illegal immigration falls under the Act’s categories, they may have legal grounds to proceed.

Ultimately, the decision on whether to involve the military in deportation efforts will depend on legal interpretations and justifications of the current immigration crisis.

George Fishman is senior legal fellow at the Center for Immigration Studies.