Solidarity will bring a case of racial discrimination against former justice minister Jeff Radebe over the promotion for magistrate Martin Kroukamp to a senior magistrate at Alberton Magistrate's Court in 2014.
The case will be heard at the High Court in Pretoria on Monday.
Solidarity contends that Radebe ignored the commission's recommendation, saying that Kroukamp's promotion would not promote transformation.
The union had subpoenaed Radebe to appear in the court, but at this stage, he had "evaded being questioned by the court".
Solidarity's Dirk Groenewald said in a statement that after Minister of Justice Michael Masutha's review, Kroukamp was not appointed. Solidarity would need to approach the registrar of the court to have the matter re-enrolled.
"The public are entitled to the best administration of justice possible. "Leaving senior posts vacant and withdrawing them later on the grounds that a white man will not promote transformation is simply unacceptable and must be fought tooth and nail," he said.
Masutha told the Equality Court in September 2014 that he would review his predecessor's decision not to appoint Kroukamp as a senior magistrate.
"Minister Masutha also undertook to review the decision to withdraw and re-advertise 22 other senior magistrate's posts," Groenewald said in a statement.