What happened in South Africa could happen in Iran as well. But everything depends on Ayatollah Ali Khamenei. He may, like former South African President F.W. de Klerk, decide to create an opportunity for transition. Or he may, as he has done in the past, choose to suppress the will of the people with violence. Millions of Iranians trust Mir Hossein Mousavi. He could play the role that Mr. Mandela played in the peaceful transition in South Africa.

If such a transition occurs, people will ask what will happen to those who perpetrated crimes against humanity, such as the mass executions committed in the name of the Islamic state. Here the precedent set by the Truth and Reconciliation Commission in South Africa can provide a possible model.

The United Nations could play a crucial role. Though the U.N. has many weaknesses, it has a strong track record in what is known as transitional justice. U.N. Secretary General Ban Ki Moon should discuss potential involvement in Iran with the Security Council. Would this be an infringement of Iranian sovereignty? No.