OTTAWA - The security-certificate case against Mohamed Harkat should be tossed out because it violates the Ottawa man's constitutional rights, his lawyer says.

Details of the federal evidence remain cloaked in secrecy, making it impossible for Harkat to defend himself, Norm Boxall said during a Federal Court of Canada hearing Tuesday.

"In my submission, the summaries we've received are not sufficient for Mr. Harkat to meet the case," Boxall said.

Harkat's legal team began two days of arguments aimed at halting the proceedings on the basis they violate his guarantees of fundamental justice under the Charter of Rights.

The Canadian Security Intelligence Service alleges Harkat, arrested in December 2002, is an al Qaeda sleeper agent with ties to several Islamic extremists.

The former gas-station employee and pizza delivery man denies any involvement with terrorism.

Harkat says he is merely a refugee who fled his strife-torn Algerian homeland and worked with an aid agency in Pakistan before his 1995 arrival in Canada using a false Saudi passport.

The government is trying to deport Harkat on a national security certificate, a rarely used immigration tool for removing suspected terrorists and spies.

The government revamped the certificate process after the Supreme Court of Canada declared it unconstitutional in 2007. Among the changes was the addition of special advocates -- lawyers who serve as watchdogs and test federal evidence against the person facing deportation.

However, the special advocates do their work behind closed doors due to the sensitive nature of the classified evidence.

Boxall said the advocates are "at a grave disadvantage" because they are severely limited in who they can speak to, the research they may conduct and witnesses they can call. "There's a whole host of hurdles."

In addition, Boxall argued there were few specifics of the federal case against Harkat on the public record.

He said this continues to leave his client to fend off accusations, such as the federal assertion he visited Afghanistan, with no details of the timing or circumstance.

"All Mr. Harkat can do is deny it."

Lawyers for both Harkat and the government have spent weeks cross-examining witnesses in public hearings that will help determine whether Justice Simon Noel upholds or strikes down the security certificate.

Federal lawyer Bernard Assan scoffed at the notion Harkat is in the dark.

"To say he doesn't know the case to meet makes a mockery of everything that has happened here," he said.

"Mr. Harkat knows the allegations against him."

Assan questioned whether details such as precisely when Harkat is said to have been to Afghanistan -- a trip he denies making -- would help his case.

"I that going to change his answer?" No," Assan said.

"Being to Afghanistan is not something that slips your memory."

Noel offered hints of support for the arguments of both sides.

The judge said specific information could help Harkat -- for instance, an overheard statement that cast him in a bad light might have been a mere joke.

On the other hand, Noel cast doubt on making full disclosure of the evidence in a certificate case to the person accused of being a security threat - especially an alleged spy.

"I think that would be counter-productive to the interests of all Canadians."

It is not clear when Noel will rule on the constitutional arguments.

The court plans to continue looking at the allegations against Harkat in late May with a final week of hearings on whether the substance of the certificate case passes muster.