The judge said the parole conditions must be announced by no later than 5 June.
Judgment was handed down after Derby-Lewis filed an urgent application.
Derby-Lewis was sentenced to life in prison for the killing of South African Communist Party leader Chris Hani in 1993.
The 79-year-old has already served 21 years in jail but was recently spending time in a prison hospital after being diagnosed with cancer.
On Monday, the 79-year-old’s legal team argued that he only had two months to live as he suffers from terminal cancer.
