It doesn’t take a legal expert to know that what’s happening in Portland, Oregon is an abuse of power. When unidentified federal forces dressed as soldiers pull people off the streets into unmarked vans, something is gravely wrong. What’s less apparent is that this abuse is part of an ongoing effort by the administration to get around “posse comitatus”: the principle that the president cannot use the military as a domestic police force. The implications for the rule of law — and potentially for the 2020 election — are staggering.