The Democratic Alliance's (DA) challenge to government's decision to withdraw from the International Criminal Court (ICC) will be heard in the High Court in Pretoria on Monday.
Last month, the Constitutional Court dismissed the party's application for direct access to challenge the decision.
On October 21, Justice Minister Michael Masutha told reporters that South Africa had initiated the process of withdrawing from the ICC by notifying the United Nations of its intention to revoke its ratification of the Rome Statute, which established the ICC.
The decision followed several court judgments that the government violated the law by not arresting ICC-indicted Sudanese President Omar al-Bashir during his visit to South Africa in June last year.
DA federal executive chairperson James Selfe previously said Cabinet's decision was "unconstitutional, irrational and procedurally flawed".
"The decision by [International Relations] Minister [Maite] Nkoana-Mashabane to act unilaterally on this matter is a disgrace and shows the depth of impunity and disregard for the rule of law within the ANC," he said.
"Clearly she has taken her lead from President Jacob Zuma."
The Constitution is clear that binding international agreements become law upon ratification by Parliament, he said.
"It is thus unconstitutional for the minister to unilaterally exit South Africa from the agreement without Parliament having repealed the agreement first."