Aides scrutinized, sometimes blocked release of documents requested under public-records law WASHINGTON—When Hillary Clinton was secretary of state, her staff scrutinized politically sensitive documents requested under public-records law and sometimes blocked their release, according to people with direct knowledge of the activities. In one instance, her chief of staff, Cheryl Mills, told State Department records specialists she wanted to see all documents requested on the controversial Keystone XL pipeline, and later demanded that some be held back. In another case, Ms. Mills’s staff negotiated with the records specialists over the release of documents about former President Bill Clinton’s speaking engagements—also...