Senior aides to President Trump have restricted the number of administration officials allowed to listen to his phone calls with world leaders, according to CNN. The new restrictions are part of an ongoing tightening of access to the inner circle around the president after the disastrous July 25 phone call between Trump and Ukraine president Volodymyr Zelensky. During the phone call, which has formed the focal point of ongoing impeachment hearings, the president appeared to threaten to hold back military aide if Ukraine refused to investigate his political rival and former vice president Joe Biden and his son Hunter. “Nobody is allowed on the calls,” a White House official told CNN. “The barn door officially closed after the horse escaped.”