Conservative Leader Andrew Scheer is registered with the U.S. Selective Service System, the federal agency that administers that country's military draft, a party spokesperson confirmed Friday.

Scheer confirmed Thursday that he is a dual Canada-U.S. national — his father was born in the U.S. — but said he is in the process of renouncing his American citizenship.

When asked today why he never made his dual citizenship public, Scheer said nobody had ever asked him about it.

"Everyone who knows me or knows my family knows that my father was born in the United States," Scheer said.

Under U.S. law, all American men between the ages of 18 and 26 must register with the Selective Service System, the U.S. federal agency that maintains information on men who could be conscripted into the military through a system known as "the draft."

Scheer was asked today at a campaign event if he had ever registered with the service. He replied that he couldn't say for certain. A party spokesperson later confirmed Scheer had filed the necessary paperwork.

"Mr. Scheer registered as required by law," Simon Jefferies, a spokesperson for Scheer, said in an email.

Registration allows the U.S. government to compile a list of individuals who can be pressed into service in the event of a national emergency, or when "a rapid expansion of the armed forces is necessary," according to the Selective Service System website.

That website also says "non-citizen and dual national men MUST still register with the Selective Service System. They are not exempt from the registration requirement."

Failing to register is a felony punishable by a fine of up to $250,000 or a prison term of up to five years, or a combination of both.

Scheer called his dual citizenship a non-issue, given how many other Canadians hold two passports.

"It's not a big deal for people to have dual citizenship," Scheer said. "There are millions of Canadians who have had a parent born in one country or another. And I've always been tax compliant. I've always followed those laws."

Scheer said he made the decision to formally begin the process of renouncing his citizenship in August 2019. He said he has not held a valid U.S. passport in years.

The U.S. State Department website advises all U.S. nationals, including dual nationals, that they "must use a U.S. passport to enter and leave the United States."

If [Scheer] does win the election, he's still going to be an American citizen. It takes months. - U.S.-based immigration lawyer Len Saunders

When asked Friday about his U.S. passport, Scheer said he couldn't recall when he last used the American travel document.

"I would have to go back and look," he said. "I have never needed my passport as an adult."

Scheer has travelled to the U.S. in his capacity as the leader of the Official Opposition. He made at least one trip to Washington during the contentious NAFTA negotiations.

A spokesperson for U.S. Customs and Border Protection (CBP) said any American person — including those with dual citizenship — travelling to the U.S. must inform border guards that they are a U.S. national upon entry.

"U.S. citizens should present themselves as such, otherwise grounds of inadmissibility may apply," Stephanie Malin said in an email to CBC News.

Washington-based immigration lawyer Len Saunders told CBC News that Scheer would "absolutely [be] considered an American under immigration laws."

"Just because his passport is lapsed doesn't mean he's not an American," he said. "I'm surprised he didn't renounce his citizenship a long time ago.

"If he does win the election, he's still going to be an American citizen. It takes months."

Liberal Leader Justin Trudeau said Scheer should have been upfront about American citizenship.

"I think there is nothing about having a dual citizenship that should disqualify anyone from being a politician. But I do think that you have to be honest with Canadians when you're applying for a job to be the prime minister for thirty seven million Canadians. I think that's what Mr. Scheer has to answer for," Trudeau said.

Liberal Leader Justin Trudeau says Andrew Scheer is not being honest with Canadians over his dual citizenship. When challenged by a reporter at a campaign stop in Quebec about whether he was dishonest about wearing blackface, Trudeau says he "took responsibility for his mistakes in the past." 0:44

U.S. citizenship comes with many rights and privileges — the freedom to live, work and vote in the world's largest economy — but it also carries unique responsibilities that the U.S. demands of its citizens.

For example, under U.S. tax law, an American citizen living anywhere in the world must report their global income and file returns with the Internal Revenue Service (IRS). U.S. citizens must file income, estate and gift tax returns with the IRS.

Scheer has said he has filed U.S. tax returns.

Moreover, under the Foreign Account Tax Compliance Act, all U.S. citizens also must tell federal authorities about their foreign accounts, such as bank accounts, brokerage accounts and mutual funds.

Those American citizens must file a report of Foreign Bank and Financial Accounts, or FBAR, with the Treasury Department's Financial Crimes Enforcement Network.

There's a $12,921 penalty for non-willful violations, while individuals who deliberately evade the law could face fines of up to $129,210, or 50 per cent of the account's value.