The federal government will have to prove a 92-year-old Waterloo man was a willing participant in the activities of the Nazi death squad he worked for during the Second World War if it wants to kick him out of the country.

The Supreme Court ruled Thursday it will not hear the federal government's appeal of a lower court's decision telling the government to reconsider the decision to revoke Helmut Oberlander's citizenship.

"Now it goes back to the governor in council to make a decision to consider again, for the fourth time, whether to take away the citizenship of a man who was involved in the war against his will and who did not commit war crimes," Oberlander's lawyer Barbara Jackman told CBC's Alison Crawford.

Oberlander forcibly conscripted

Jackman maintains Oberlander, who was born in Halbstadt, Ukraine in 1924, was forcibly conscripted by the Nazis when he was 17. He served as an interpreter for Einsatzkommando 10a, a group of mobile killing squads that targeted Jewish people.

The federal government has argued Oberlander failed to disclose his activities during the Second World War to Canadian officials when he obtained his citizenship in 1960. He worked as a building developer in Waterloo region.

Helmut Oberlander

Helmut Oberlander has said he was forcibly conscripted by the Nazis when he was 17 years old. (CIJA)

The federal government has revoked his citizenship three times, the first time in 1995. He remains in the country during legal proceedings.

Guilt by association not enough

In the years since the government first moved to try and take away Oberlander's citizenship, the Supreme Court of Canada has decided in another case – Ezokola v. Canada – that the government has to prove the person contributed to the crime or a criminal organization.

In that 2013 case, the court found guilt by association was not reason enough to deny refugee status to Rachidi Ekanza Ezokola, a former diplomat from the Democratic Republic of Congo during years when the government was responsible for a number of atrocities including the massacre of civilians and recruitment of child soldiers.

Jackman said that means now the government will have to prove Oberlander was in some way complicit in the war crimes of which he is accused.

'He should be deported'

In April, several Jewish groups called on the federal government to keep the pressure on to remove Oberlander from the country.

"Mr. Oberlander was a member of Einsatzkommando 10a, a Nazi mobile killing unit responsible for the murder of tens of thousands of Jews," Shimon Koffler Fogel, CEO of the Canadian Centre for Israel and Jewish Affairs wrote in a release. "He lied on his citizenship application and gained access to Canada fraudulently. Based on these facts, neither of which are in dispute, he should be deported."

Nate Leipciger, a Holocaust survivor and past co-president of Canadian Jewish Holocaust Survivors and Descendants, said the government needed to pursue the case.

"Let us all speak as united voices and on behalf of the victims and survivors and let the government know that there is no time limit nor age consideration to bring the guilty to justice," he said in the April release. "The few remaining survivors are still suffering the loss of our loved ones and remember the brutality of the Einsatzkommando 10a and the murder of tens of thousands. Do not extend our anguish by inaction."

with files from Alison Crawford