At-risk Aboriginal children placed in non-Aboriginal homes during the Sixties Scoop may well have suffered harm by losing their cultural identities but the federal government cannot now be held liable, Ottawa argues in new court filings.

As a result, the government plans to press an Ontario Superior Court justice on Thursday to dismiss a landmark $1.3-billion class action, filed on behalf of thousands of those children in 2009, that argues Canada failed to protect their cultural heritage with devastating consequences.

"On-reserve Indian children who were determined to be in need of protection and were, as part of the child-protection regime of the day, placed in non-Aboriginal foster homes or raised in non-Aboriginal adoptive homes (would) have lost opportunities to remain connected to their families and to their language and culture," the attorney general states.

"Many foster and adoptive children faced with such circumstances experienced psychological or other personal harms."

However, while things might be done differently now, the government argues, no legal reason exists to apply modern standards to an approach taken decades ago.

Old newspaper clippings promote adoption of First Nations children. (Karen Pauls/Twitter) The Sixties Scoop in which an estimated 16,000 Aboriginal children ended up in non-native homes flowed from a federal-provincial arrangement in place from December 1965 to December 1984. The government says its role was to fund child-welfare programs for the native children but it was up to Ontario to provide the services.

In response to Ottawa's arguments, the lead plaintiff accused the government of deliberately missing the point entirely, and disputed the notion that the lawsuit was trying to impose today's standards and values on a past situation.

"Canada was fully aware during the class period of the frustration, anger, disappointment and concern of the post-placement effect upon these children," Marcia Brown Martel says in her reply factum.

The key issue, she asserts, is that the government ignored an obligation to consult with Aboriginal bands about the placements and did nothing for the children after they were taken from their homes.

"Canada took no steps to assist the adopted child post-adoption," Brown Martel says. "Canada provided no services other than a useless adoption booklet, which went nowhere other than to ministerial offices."

The plaintiffs also accuse the government of playing litigation games by trying to advance arguments without putting forward any evidence to back them up, and with last-minute filing of materials.

Raven Sinclair, associate professor of social work at the University of Regina and a Sixties Scoop adoptee, says indigenous families' ability to raise children was decided on by social workers who were primarily young, white and middle-class. 1:03 Brown Martel, a member of the Temagami First Nation near Kirkland Lake, Ont., was adopted by a non-Aboriginal couple in 1972 at age nine. She later discovered the Canadian government had declared her original identity dead.

At the start of the hearing before Superior Court Justice Edward Belobaba in August, scores of Aboriginal people from across Ontario rallied outside the courthouse to denounce what they called the "cultural genocide" perpetrated by the government against Indigenous people.

In court that day, the plaintiffs' lawyer Jeffery Wilson said the '60s Scoop may have been part of the government's hidden agenda to "remove the savage Indian from the child," although what exactly motivated the "abomination" was not clear.

The unproven claim seeks $85,000 for each affected person on the basis that the children suffered emotional, psychological and spiritual harm due to the loss of a cultural identity that Canada negligently failed to protect.

Brown Martel wants Belobaba to find in her favour based on the evidence already before him, while the government maintains there's no legal basis for her claim and wants it tossed without further ado.