The country's ten-thousand-strong prison population can't vote in this year's election.
But a Court of Appeal decision has found this is unfair and unjustified.
It was Auckland Prison inmate Arthur Taylor who originally took the case to court with other prisoners and says he's "over the moon" about the decision.
In 2010 the Government changed the law so prisoners couldn't vote. Before that, only prisoners serving more than three years were banned.
Speaking to the Nation last year from prison, Mr Taylor explained why he took the Government to court over the law change:
"Who's going to be next? Maybe homosexuals, maybe the next unpopular person that comes along who they can label. Mental defectives, refugees, who knows?
"The moment they start creating a precedent, then you have to step in and do whatever the hell you can to stop it."
But Mr Taylor hasn't stopped it. The law stands - prisoners still can't vote.
However the Court of Appeal decision has found the law is inconsistent with the Bill of Rights.
"The Government should closely study the Court of Appeal judgement and bite the bullet; accept that this is bad law", Mr Taylor says.
Even though the court has made their view very clear, the Government doesn't have to take action.
"If they raise significant policy issues we'd look at them, but up until now we haven't seen a reason to change the law", Bill English says.