The Supreme Court has reserved its decision relating to charges laid against former MP Phillip Field.
Field was jailed for six years in 2009 after being found guilty of 11 counts of bribery and corruption and 15 of attempting to pervert the course of justice.
He is the first politician in New Zealand to be convicted of corruption.
The charges were laid after he accepted labour from Thai people he had helped with immigration matters, then tried to cover that fact up during an official inquiry.
Last year, the Court of Appeal dismissed Field's appeal against conviction and sentence, but earlier this year the Supreme Court indicated it would hear an appeal relating solely to the bribery charges.
On Tuesday, his lawyer Helen Cull, QC, told the Supreme Court that the Appeal Court had found there is no such offence as bribery and corruption by an MP under New Zealand law.
She said that court had redefined the charge as corruptly accepting a bribe.
Ms Cull said for Field to be guilty of that, he would have had to ask the Immigration Minister to consider only the Thai people's immigration applications and disregard those of other races, but he had not done that.
However, Solicitor-General David Collins told the court the Crimes Act refers to any act done by an MP, which includes rewards - such as those Field received for providing immigration assistance to the Thai workers.
The issues the Supreme Court considered whether Field was deprived of the right to a fair trial as a result of evidence from the official ministerial inquiry being produced at his trial.
