The provisions of this subchapter shall not be applicable with respect to any person against whom there is pending a criminal charge, whether by indictment or by information, which has not been fully determined or who is on probation or whose sentence following conviction on such a charge, including any time on parole or mandatory release, has not been fully served, except that such provision shall be applicable to any such person on probation, parole, or mandatory release if the authority authorized to require his return to custody consents to his commitment.