OTTAWA -- Alexander Vavilov, the Toronto-born son of Russian spies, breathed a sigh of relief Thursday after the Supreme Court declared him a Canadian citizen and ended a long-running legal battle.

In its judgment, the high court upheld a Federal Court of Appeal decision that effectively affirmed the citizenship of not only Alexander but also his brother Timothy.

"The relief I feel reading the Supreme Court's decision is indescribable," Alexander said in a statement issued by his lawyer. "It is recognition that not only do I feel Canadian, but I am Canadian in the eyes of the law."

Aside from addressing the citizenship matter, the Supreme Court ruling aimed to bring clarity to the nature and scope of judicial review of decisions by administrative officials.

Alexander, 25, and Timothy, 29, were born in Canada to parents using the aliases Donald Howard Heathfield and Tracey Lee Ann Foley.

The parents were arrested nine years ago in the United States and indicted on charges of conspiring to act as secret agents on behalf of Russia's SVR, a successor to the notorious Soviet KGB.

Heathfield and Foley admitted to being Andrey Bezrukov and Elena Vavilova. They were sent back to Moscow as part of a swap for prisoners in Russia.

Alexander, who finished high school in Russia, changed his surname to Vavilov on the advice of Canadian officials in a bid to obtain a Canadian passport.

But he ran into a snag at the passport office and in August 2014 the citizenship registrar said the government no longer recognized him as a Canadian citizen.

The registrar said his parents were employees of a foreign government at the time of his birth, making him ineligible for citizenship.

The Federal Court of Canada upheld the decision.

But in June 2017, the appeal court set aside the ruling and quashed the registrar's decision. It said the provision of the Citizenship Act the registrar cited should not apply because the parents did not have diplomatic privileges or immunities while in Canada.

On the strength of the ruling, Alexander has since been able to renew his Canadian passport and he hopes to live and work in Canada -- calling his relationship with the country a cornerstone of his identity.

In its decision, the Supreme Court said the registrar's decision was unreasonable. Although the registrar knew her interpretation of the provision was novel, she failed to provide a proper rationale, the court said.

"She offered no justification for the interpretation she adopted except for a superficial reading of the provision in question and a comment on part of its legislative history," the decision said.

On the other hand, there is overwhelming support -- including in parliamentary debate and established principles of international law -- for the conclusion that lawmakers did not intend the Citizenship Act provision to apply to children of people who have not been granted diplomatic privileges and immunities, the court added.

Although it involves the same central issue, Timothy's case proceeded separately through the courts and was therefore not directly before the Supreme Court.

However, in a decision last year, the Federal Court said the ruling on Alexander equally applied to Timothy, making him "a citizen."

Timothy has also been able to renew his Canadian passport, said lawyer Hadayt Nazami, who represents the brothers.

Alexander plans to hold a news conference Friday in Toronto.

Nazami said the younger brother's "profound ordeal in the past decade has shown us that wrongful denial of the right of citizenship by birth is too high of a cost for a person to bear."

The case and another ruling Thursday, involving the federal broadcast regulator, gave the Supreme Court an opportunity to set out new standards for reviewing administrative decisions.

Whenever a court reviews an administrative decision, it should begin with the presumption that the applicable standard of review is reasonableness, the court said. "To be reasonable, a decision must be based on reasoning that is both rational and logical."

However, there are cases when the reasonableness standard will not apply. These include instances where a legislature has indicated it intended a different standard of review or has set out a statutory means of appealing a decision.

In other cases, the rule of law will require that the standard of correctness apply -- for example, when uniform and consistent answers are needed on general questions of law that are of central importance to the legal system, the court said.

This report by The Canadian Press was first published Dec. 19, 2019.