Bruce Montague — a former firearms dealer and pro-gun activist — was charged with several firearms offences in 2005 after he refused to obtain a licence to own and sell weapons as an act of protest against gun laws at the time.
He was convicted and sentenced to 18 months in jail in 2008 on 26 firearm-related offences.
In 2004, police seized more than 200 firearms from Montague, some which had been modified into automatics and others which had their serial numbers removed.
They also seized accessories worth upwards of $100,000 along with more than 20,000 rounds of ammunition.
The items had been held by police since then and the Crown later filed a forfeiture order to take possession of the items for good.
Montague took his case to the Ontario Court of Appeal, but it rejected his argument that the seizure sought by the Crown amounted to cruel and unusual punishment under the Charter.
Ontario's top court ruled that Montague and his wife made the choice to flout firearms-licensing rules.
It had also found that the situation could have been far more dangerous if Montague's modified weapons had fallen into the hands of criminals.
Montague then sought to appeal the ruling at the Supreme Court of Canada, but that effort was dismissed on Thursday.
In keeping with standard practice, the Supreme Court of Canada gave no reason for its decision.
"They are beaten down and discouraged," said Derek From, a lawyer with the Canadian Constitution Foundation, which has been supporting the Montagues through their legal battles.
"They feel that they long ago paid for the allegedly criminal act of not doing paperwork."
Lawyers for Montague had planned to argue at the Supreme Court that a section of the Charter of Rights and Freedoms which forbids the imposition of "any cruel and unusual treatment or punishment" applies to mandatory property forfeiture.
"I had hopes that the Supreme Court would hear this appeal because as it stands right now forfeiture legislation is being handled in slightly a chaotic way throughout the country," From said.
"Different courts of appeal throughout the country are coming to basically divergent results on similar matters. This was an opportunity for the Supreme Court to unify what's going on in forfeiture's throughout Canada."
Montague and his wife's battles aren't over yet. The province of Ontario is seeking to confiscate their home under the Civil Remedies Act, said From.
"Ontario believes that their house is either the instrument of crime or the proceeds of crime," he said.
That case had been on hold as the couple's criminal case worked its way through the courts, and From said the Montagues plan to fight to keep their home.