More than seven years after he was arrested, Kim Dotcom will make his final stand against extradition to the United States in New Zealand's Supreme Court today.

The United States Department of Justice has been trying to extradite the internet entrepreneur and his fellow-accused - Mathias Ortmann, Bram van der Kolk and Finn Batato - since 2012, to face criminal charges related to their defunct file-sharing website Megaupload.

North Shore District Court found in December 2015 that the men were eligible for extradition but they have fought the decision every step of the way, unsuccessfully appealing to the High Court and then the Court of Appeal.

Both higher courts criticised the district court's decision-making process but ultimately confirmed its finding.

If the Supreme Court also upholds the finding after a week-long hearing beginning today, it will be referred to Justice Minister Andrew Little to make the ultimate decision.

Dotcom, Ortmann, van der Kolk and Batato were arrested on 20 January, 2012, during a dramatic armed raid on the rural Auckland mansion Dotcom was renting at the time.

The group has maintained in court hearings for the past seven-and-a-half years that Megaupload was created to allow people to store and share large files.

But the FBI, which co-planned the raid with its New Zealand counterparts, claimed the site wilfully breached copyright on a mass scale by hosting illegally-created movie, music and software files.

The agency said the site aided and abetted users who uploaded such files by paying them rewards.

This week's Supreme Court hearing is likely to hinge on whether the actions the men are accused of count as crimes under New Zealand law, either through the Copyright Act or the Crimes Act.

Their behaviour has to be considered criminal in New Zealand as well as the United States for extradition to go ahead.

Canterbury University law professor Neil Boister, who specialises in extradition law, said the Crown - which represents the US in New Zealand - had a much easier task this week than the men's legal team.

Crown lawyers only needed to successfully argue that at least one of the counts on the US indictment is also a crime in New Zealand, and that there was preliminary evidence of the men's behaviour, in order to prevail.

"If they get over this hump, he's probably gone."

If the Supreme Court decision did not go in Dotcom's favour, and the Justice Minister decided he should be extradited, a judicial review of the minister's decision offered one last narrow window of escape, Boister said.

"The difference with the judicial review is that you can introduce all sorts of material that's not evidence," he said.

That could include arguments about whether extraditing the men could amount to a breach of their human rights.

"You could introduce Amnesty International reports about the conditions in the US jails and so on."

This week's appeal will be heard by a full panel of the five Supreme Court justices.