The Supreme Court of Canada has ruled that a "flagrant" breach of a key treaty signed with indigenous peoples over a century and a half makes a "mockery" of the agreement and deprives generations of fair compensation for their resources.

In a unanimous decision, the court accused the governments of Ontario and Canada of grossly violating and "making a mockery" of the spirit and substance of the Robinson Treaties for 150 years.

"For nearly a century and a half, Anishinaabe peoples have been left with the broken promises of the treaty," the court said.

The Robinson Treaties, signed in 1850 between the Anishinaabe Indian tribes and the British Crown, regulate the hunting and fishing rights of indigenous communities over an area of more than 35,700 square miles.

The agreement calls for yearly increases in annual payments as the land brings more wealth to local communities.

According to the agreement, each native received 1.70 Canadian dollars per year. In 1875 the rate was raised to $4 per person and has not been raised since.

The justices said that while the amount of money in the contract was not guaranteed, "neither party doubted that the Crown could, and ought to, have raised more than $4 per person without loss of annual profit."

The court called for a "return to treaty fundamentals" and "protection of the honor of the Crown" by increasing annual fees. Failure to do so would be "outright dishonesty," the judge wrote.

The Supreme Court gave Ontario six months to propose a new deal with indigenous groups and warned of intervention if the governments can't agree on fair compensation.

"If the Crown and superior plaintiffs are unable to reach a negotiated settlement, the Crown will require the Supreme Plaintiffs to compensatory damages for their past wrongdoings within six months of the date of notice of these reasons," Friday's order said.

Indigenous peoples themselves claim they are owed C$126 billion in overdue payments. The government has billed the "costs of colonization" in the billions and denied its debt to the indigenous peoples.

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