Foreigners detained on security certificates will have a new voice with the creation of special advocates to argue their case, says Canada's Public Safety Minister Stockwell Day.

The rarely used but controversial security certificates were deemed unconstitutional by the Supreme Court of Canada in February.

One of the changes the court requested was an amendment to the legislation to make provision for special advocates who would represent those held on the certificates.

The government reintroduced the legislation on Monday with the new provision added.

Critics of the measure say that while the advocates will have access to the information being used to hold the detainees, they won't have the freedom to confer with their clients about the details.

Day argued that point, saying the advocates will be able to make a court challenge on any of the information they disagree with. But he conceded they will only be able to give a summary of that information to their client and won't be able to discuss specific points.

In effect, it means the detainee may never know why they are being held.

"We're not going to allow the list of the men and women who work hard to keep our country safe to be shown to somebody who has been deemed to be so dangerous to be in this country that, in fact, they're being detained," Day told CTV's Canada AM on Tuesday.

"The other thing that we need to recall is this does not apply to Canadian citizens. It applies to somebody who comes to the country whose background shows they are so dangerous that they need to be detained while they're appealing their refugee status. But at any time they are free to leave the area of detention and go back to their country of origin."

Day said the process has only been used six times since 2001 when it was introduced. In each case, the government convinced the federal court the person could put Canadians at risk, and should be detained while their refugee claim was being reviewed.

He also pointed out that it's not a trial process, but is part of the refugee claimant system, and detainees can opt out and return to their home country at any time.

However, advocates feel the new measures simply aren't fair. Paul Copeland, the lawyer representing Mohamed Harkat, who has been held on one of the controversial certificates since 2002, said the new measures don't go far enough.

"They have adopted a very bare-bones model of a special advocate," Copeland told Canada AM.

"They learned nothing of what happened from England so the special advocates are left with no assistance, there's no research facility to help the special advocate. Special advocates are restricted, as in England, in talking to the person. So how the person ever gets to know the case they have to meet is still beyond me."

As a lawyer, Copeland said he defended two men held on security certificates before the Supreme Court of Canada. In both cases, he knew nothing about the evidence against his clients.

While the advocates are intended to solve that problem, he expressed doubts that it will work.

"The special advocate will probably see all of the evidence but the person concerned will probably know none of it," Copeland said.

"And if the special advocate can't go back and talk to the person and say, and one of the issues is --Were you in Afghanistan in January of 1993 -- if they can't go back and talk to the person and find out, they may never be able to present the case effectively in the secret hearings before the judge."