An application to appeal against the sentence conversion of two of the "Waterkloof four" was dismissed by the Pretoria Regional Court on Friday.
Reinach Tiedt and Gert van Schalkwyk would remain under house arrest after their 12-year sentences for murder and assault were converted on December 15 last year.
The application was brought by the correctional services commissioner. In dismissing it, magistrate Peet Johnson said: "The commissioner has no authority to interfere with the decision of the parole board."
The commissioner was ordered to pay the respondents' costs.
Johnson said a representative of the Directorate of Public Prosecutions (DPP), who was also the prosecutor in the Waterkloof case, attended the conversion application in December 2011.
The DPP representative at the time did not object and said the application was correct and well prepared.
"If the DPP did not oppose the application, why would the commissioner?" Johnson asked.
He said advocate M Sithole, for the commissioner, presented the court with an outdated version of the law that applied in the case.
Sithole contended the commissioner had the right to appeal the sentence. Johnson corrected him and said the parole board and commissioner had equal rights.
Sithole argued that the relatives of the deceased, a homeless man, should have been notified of the sentence conversion. Johnson said the victim was never identified and no relatives could be found.
Sithole argued that the commissioner did not know of the conversion hearing. Johnson asked how he could not have known if the two applicants were brought to court and guarded by about 10 correctional services officers.
Tiedt and Van Schalkwyk were among a group of four boys convicted of killing a homeless man and assaulting another at a park in Pretoria in 2001. They began serving their sentence at the Pretoria Central Prison in 2008.