The United States Government earlier this year won a civil forfeiture case against Megaupload and its founder, Mr Dotcom, who they argued was a fugitive.
As a result, the online mogul has lost an estimated $67 million worth of assets to the US including millions in cash, property, luxury cars, jet skis, large screen televisions and art.
Mr Dotcom has appealed against the decision, claiming a violation of basic rights and due process.
The Cato Institute, National Association of Criminal Defense Lawyers and the Institute for Justice have filed an independent brief in support of Mr Dotcom and other Megaupload defendants. Read it here.
"The present case concerns amici because the federal government's aggressive use of forfeiture poses a grave threat to property rights and can cause irreparable injury when property is forfeited without any hearing," the legal document states.
"Stripping the claimants of their due process rights isn't just unconstitutional, it's dangerous. There's a growing literature on the abuse of civil forfeiture - and those abuses are directly tied to the protections given to the claimants here, as well as the ability of government officials to directly benefit from forfeitures. This court should not ratify a doctrine that would make abuses even easier."
In a blog published on its website, the American libertarian thin-tank Cato Institute sites the Fifth Amendment's due process clause, which "requires an opportunity to be heard and an opportunity to defend" against government-initiated actions against an individual's property.
"Unlike an escaped criminal appellant who is scorning the court's jurisdiction, in civil forfeiture, it's the government that has dragged Dotcom and the others into court," it says.
"Moreover, given the amount of abuse in civil-asset forfeiture, the government shouldn't be allowed both to profit from the forfeiture and suppress defenses by calling residents of other countries 'fugitives'."
It says the courts should not only allow Mr Dotcom and the other Megaupload defendants to challenge the seizure, it should also consider "striking down as unconstitutional" all uses of fugitive disentitlement in civil-forfeiture cases.
Mr Dotcom told filesharing news website Torrent Freak that he welcomed the support.
"It is good to see that there are groups of legal experts in the United States that hold the Government to account and combat the abuse of power and prosecutorial overreach," he said.
Mr Dotcom was controversially arrested in January 2012 at his Coatesville mansion near Auckland on behalf of the US, which wants him to stand trial on copyright and money-laundering charges, which he denies.
An extradition hearing is set down for September this year.
- By Kurt Bayer of NZME News Service
