William Banks spoke with HowStuffWorks about the Posse Comitatus Act, a federal statute prohibiting use of the military in civilian law enforcement, and President Trump's recent order to send troops to the southern border. "Posse comitatus isn't the only legal problem. Everything that the United States does has to be based on some legal authority," says Banks. "It's not clear to me what the legal authority is to even send the military down there. [Trump] hasn't said, and no one else has said, other than 'We need them down because we got some bad people coming at us on the border.' That's not a legal theory." 11/30/18