Federal officers using large amounts of tear gas against protesters in Portland, Oregon on July 21.John Rudoff/Anadolu Agency via Getty ImagesSarah J. Adams-Schoen, University of OregonPresident Donald Trump has announced that the U.S. Department of Justice will send a “surge of federal law enforcement” into American cities run by “extreme politicians” who are on an “anti-police crusade,” including Chicago, Kansas City, Albuquerque, Cleveland, Detroit and Milwaukee.Those cities may soon see legal battles like the ones in Portland, Oregon, where four notable lawsuits challenge the actions of fe…