A lawyer for the first person charged under Canada's Anti-terrorism Act says it is impossible for suspects to defend themselves when Canadian law allows government lawyers to meet secretly with judges to decide what evidence should be hidden from the defence.

Ottawa resident Mohammad Momin Khawaja was in federal court in Ottawa Wednesday while one of his lawyers argued against part of Section 38 of the Canada Evidence Act.

The part in question allows government lawyers to meet with the judge to discuss why certain evidence should be kept from the defence.

On Wednesday, Khawaja looked on while defence lawyer Lawrence Greenspon argued for over three hours that the process is unconstitutional and makes it impossible to mount a meaningful defence.

Outside the courtroom, Greenspon said his client has a Charter-protected right to a fair trial, and must have access to relevant evidence in order to defend himself against it and exercise that right.

"We have to be able to see it, we have to be able to attack it, we have to be able to respond to it," Greenspon said.

Government lawyers have argued that 513 documents in the case can't be fully disclosed to the defence because doing so would threaten national security and agreements with other countries.

Greenspon argued earlier that the defence should have access to those documents.

On Wednesday, Greenspon said Khawaja is concerned about his trial being delayed by constitutional challenges while he waits in jail.

"That said, you can't proceed to try somebody on a section of the criminal code that is unconstitutional," he said. "We can't be expected to go to trial where there's relevant evidence that's being withheld from us."

Khawaja, previously a resident of Ottawa's Orleans neighbourhood and a computer software operator for the Foreign Affairs Department, is scheduled to be tried in May for seven terrorism-related charges concerning his alleged role in a bomb plot against British targets.

He was one of nine people taken into custody as part of the investigation, but his arrest on March 29, 2004, was the only one that took place in Canada.

On Oct. 24, 2006, an Ontario Superior Court judge struck down a clause of the Anti-terrorism Act in relation to Khawaja's case. However, he said Khawaja should still be tried for the offences with which he is charged.