"The commission is exposing its flanks to possible legal prosecution," Johan Engelbrecht SC told a gathering of former SA Defence Force members in Pretoria.
Engelbrecht said the Durban High Court had already exonerated the SADF from any wrongdoing in training paramilitary IFP units in the Caprivi Strip.
"Now (TRC deputy chairman) Alex Boraine, who is a legal novice, is busy reviewing the court's finding. They are granting themselves rights which they don't have," Engelbrecht said.
Former Defence Minister General Magnus Malan and 19 co-accused, including senior officers and IFP trainees, were in October last year acquitted of murder charges in connection with the massacre of 13 people at KwaMakutha, KwaZulu-Natal, in 1987.
Engelbrecht said the TRC was attempting to set the court's finding aside. In doing this, the body might be defeating the ends of justice.
"Reviewing court findings is the prerogative of the Appeal Court in Bloemfontein," he said.
Engelbrecht criticised the TRC for not allowing witnesses to be cross-examined by SADF legal representatives during the hearing into the Caprivi trainees.
"How can the commission come to a reliable finding if evidence is not being tested?" he asked. "The commission is supposed to unearth the truth, but it is not conducting a proper inquiry."
Former SADF chief General Jannie Geldenhuys, who also addressed the meeting, said people often asked him how the TRC could be holding a hearing into a theme which had already been dealt with by the High Court.
"I asked an advocate. He told me bluntly that there is no judicial or any other logical explanation (and that) this is excellent example of a witch-hunt."
Malan told the gathering the Durban trial, which lasted longer than a year, had been an ordeal.
"It was an humiliating experience," he said.