Is it against the law for Trump to use the military to deport illegal migrants? Maybe not

Critics of President-elect Trump’s plan to enlist the military to help deport illegal immigrants claim it will violate the Posse Comitatus Act of 1878.But that might not be the case.The 146-year-old PCA says that “except [as] expressly authorized by the Constitution or Act of Congress,” whoever “willfully uses any part of the Army, the Navy, the Marine Corps, the Air Force, or the Space Force as a posse comitatus … to execute the laws shall be fined … or imprisoned.”At least one federal court has ruled that the PCA “makes unlawful the use of federal military troops in an active role of direct law enforcement by civil law enforcement officers.” But the Supreme Court has never so concluded, and this conventional wisdom may very well be wrong.The PCA itself is of questionable morality, as the motivation behind its passing was Southern anger following the Civil War over the use of federal troops to protect freed slaves from racist violence.Further, Congress never intended the PCA to inhibit the president’s ability to utilize the military.

Rather, it was designed to overturn the “Cushing Doctrine” — devised in 1854 by Attorney General Caleb Cushing to allow a marshal or sheriff to call for military forces who would be “bound to obey [his] commands.” Indeed, in 1882, the Senate Judiciary Committee interpreted the PCA as negating any supposed authority of federal marshals to “call upon the Army,” “have command of the Army” and “direct [it] what to do.”And 120 years later, Congress explained why the Department of Homeland Security did not violate the Act by saying that it was “expressly intended to prevent [U.S.] Marshals, on their own initiative, from calling on the Army for assistance in enforcing Federal law.” As Coast Guard officers Gary Felicetti and John Luce have explained, “the primary evil” addressed by the PCA was “the loss of control over army troops via the Cushing Doctrine,” which “permit[ed] mino...