Donald Trump has fired Attorney General Jeff Sessions and also handed oversight of special counsel Robert Mueller’s investigation into Russian election hacking to a political staffer who has previously called for Mueller to be reined in. Whether such interference is seen as permissible is likely to be a political question, said Saikrishna Prakash, a constitutional law expert at the University of Virginia. “Some people will think that will be obstruction and some will think it’s just inappropriate,” he said.