Pistorius's defence argued in the South Gauteng High Court in Johannesburg that the state's appeal of a judge's decision finding the champion sprinter not guilty of murder was unsubstantiated.
The 28-year-old Paralympian was found guilty of culpable homicide last year -- a charge akin to manslaughter -- and sentenced to five years in prison for shooting his girlfriend Reeva Steenkamp on Valentine's Day 2013.
But Pistorius's legal team say his conviction was based on facts presented during the trial, not on an interpretation of law, and therefore cannot be appealed.
It's a move legal experts described as unorthodox.
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"The whole thing is highly unusual," said Kelly Phelps, a senior law lecturer at the University of Cape Town. "This is uncharted territory."
Despite the unusual tactic, Phelps said that the defence may have a strong argument in favour of getting the Pistorius appeal tossed out, paving the way for the athlete to be released from jail this year.