A ruling that a ban on prisoners voting breaches their human rights should be overturned, Crown lawyers say.
Serial criminal Arthur Taylor successfully argued for a court declaration last year that the 2010 law that banned all prisoners from voting, no matter how long their sentence, was inconsistent with the Bill of Rights.
Under New Zealand law, Parliament can pass legislation that is inconsistent with the Bill of Rights if there are justifiable grounds for doing so.
However, the High Court ruled last year that the law was full of inconsistencies and would lead to arbitrary outcomes.
The Crown has challenged that ruling in a Court of Appeal hearing today.
At the time the legislation was being considered, the Attorney-General warned Parliament that a blanket voting ban would breach human rights, but it was passed anyway.
Taylor lost a related bid in the High Court last year to have the law itself overturned.
The court found that although there was "considerable and considered support" for Taylor's arguments, the way Parliament had passed the law was lawful.