Cape Town - International Relations and Co-operation Minister Maite Nkoana-Mashabane rejected Parliament's invitation to account for her decision to grant Zimbabwean First Lady Grace Mugabe diplomatic immunity.Nkoana-Mashabane responded to the portfolio committee on international relations' invitation in a letter dated August 28 indicating her refusal, which was only made available to the committee on Wednesday.The minister said that the initial request was made on August 23, but the Democratic Alliance then took the matter to the North Gauteng High Court the following day."As such this matter is now before the courts, and therefore deemed sub-judice. I hereby request the portfolio committee to consider this matter after the courts shall have adjudicated on it," the minister's letter reads.Sub-judice means a matter is under judicial consideration and is therefore prohibited from public discussion elsewhere.DA MP Stevens Mokgalapa, who made the initial request for the minister to appear, said it was a blatant misuse of the sub-judice rule, and did not apply in the Mugabe case.ZUMA on Grace Mugabe: I don't know the reasons for Grace Mugabe's exit"The role of oversight and accountability cannot be overruled by this sub-judice rule and this is a poor attempt by the Minister to escape accountability," he said in a statement on Wednesday.Committee chairperson Siphosezwe Masango had said the minister's letter had "slipped his mind" until the issue was raised again on Wednesday, hence the late reveal, Mokgalapa told News24.Masango was not immediately available for comment.Civil group AfriForum has also filed papers in the High Court to have Nkoana-Mashabane's decision set aside.Ramaphosa defers Mugabe decision to the courtsDeputy President Cyril Ramaphosa meanwhile refused to be drawn further on the subject of Mugabe's exit from South Africa during a question session in Parliament on Wednesday.ALSO READ: Ramaphosa responds on Grace Mugabe, Muthambi, unemployment, racismRamaphosa deferred the matter to the courts, and did not want to take a stance publicly."On this matter, the minister has taken a decision," Ramaphosa said. "What we should do is allow the courts of our country... to be the arbiters."This is a difficult one and we would like the courts to rule on this. I would like the courts to rule decisively on this matter so we can know how to act in the future."He repeated many times that the ANC government believed in the human rights of its citizens, to the groans of many in the opposition benches.Inkatha Freedom Party MP Mkuleko Hlengwa asked why the courts always had to tell the African National Congress government what to do.Mugabe was accused of assaulting 20-year-old South African Gabriella Engels with an extension cord in the Johannesburg hotel where her two sons were staying on August 13.She returned to Zimbabwe on August 20 following Nkoana-Mashabane's decision.