John Edward Mitchell last year pleaded guilty to numerous crimes after 133 items, including guns, ammunition and gun parts, were seized under a court-issued abatement order designed to manage the unsanitary conditions caused by the items he amassed at his property.

Mitchell, a long-time shooter, was last month handed a suspended jail sentence and ordered to serve a four-year good behaviour order.

The matter returned to the ACT Supreme Court this week after prosecutors moved to have the guns confiscated as criminal assets.

Court documents said Mitchell developed a fascination with guns when he was a teenager and went on to become a member of the Army Reserve and the ACT branch of the Sporting Shooters' Association of Australia.

He claimed he took the guns home to practise techniques but never fired them outside a proper gun range.

ACT Health officers and police visited his home in May last year to enforce the order and check for firearms since a previous NSW firearms licence was revoked when he moved to the territory.

Police officers found an empty firearms safe and seized firearms including seven rifles, a shotgun, a revolver, a pistol and an air rifle.

They also confiscated live ammunition and ammunition components such as projectiles, caps and gun powder found throughout the house.

The man's house was in a significant state of disarray and many goods had been hoarded. Junk, firearms and ammunition were strewn throughout, according to court documents.

In an interview with police, Mitchell admitted to owning the guns and ammunition and that he was not authorised to possess the handguns.

He previously held an ACT firearms licence that was cancelled in 2000.

Mitchell initially challenged the application for items to be seized, arguing it was unconstitutional on the grounds the government's attempt to acquire his property was not on just terms.

That provision, however, did not apply to the ACT, Justice Richard Refshauge said.

Mitchell also argued that the ammunition seized, including magazines, reloading equipment and scopes, were not tainted property and should not be handed over.

In a decision published on Monday, Mr Refshauge ordered the firearms, bags and accessories be forfeited, while some reloading equipment could be returned.

Mr Refshauge said given Mitchell's mental disorder, and his long history of possessing firearms, there could be no assumption that the ammunition found at the house was for the guns also discovered there and could not be linked to the offences.

But he said the ammunition could not be handed back to Mitchell given he didn't have a gun licence, which, given his convictions, he was unlikely to gain in future.

He noted there would not be anything to stop a proposal from Mitchell's defence team for police to give the ammunition to a hunting supplies shop.