A High Court judge will decide whether a career criminal can continue his fight to win prisoners the right to vote.
Arthur Taylor and four prisoners at the Christchurch Women's Prison want the High Court to declare that the legislation breaches the Bill of Rights.
The Attorney-General and the head of the Department of Corrections are seeking to have the application struck out, saying it is an abuse of process.
John Pike, QC, the lawyer for the Attorney-General, said there was uncertainty as to whether the court had the power to say Parliament acted unlawfully when it passed the law.
Mr Pike said judges can comment on laws, but making a declaration would create a conflict between the courts and Parliament.
Justice Brown reserved his decision on Tuesday afternoon.