OTTAWA -- A terror suspect has one less legal avenue to try to stave off deportation after the Supreme Court of Canada refused to hear his appeal.

The federal government is trying to remove Mohamed Mahjoub, 58, using a national security certificate, claiming he was a high-ranking member of an Islamic terrorist organization.

The Supreme Court decision, handed down Thursday without explanation, is the latest setback for Mahjoub in a case that stretches back almost two decades.

Counsel for Mahjoub had no comment and it was not immediately clear what would happen next.

The Egyptian-born man, married with three children, came to Canada in 1995 and attained refugee status.

He once worked as deputy general manager of a farm project in Sudan run by Osama bin Laden, who would later spearhead the Sept. 11, 2001, attacks on the United States.

Mahjoub was arrested in June 2000 after being interviewed by Canada's spy agency on six occasions between August 1997 and March 1999, each time denying any involvement in Islamic extremism.

He was arrested in June 2000 under a security certificate -- a rarely used immigration tool for deporting non-Canadians considered a risk to the country.

The Supreme Court ruled the certificate process unconstitutional in 2007 and the government subsequently revamped the law, issuing a fresh certificate against Mahjoub the following year.

In 2009, Mahjoub was released from prison on strict conditions, which have since been relaxed.

The Federal Court found the security certificate to be reasonable, a conclusion upheld last year by the Federal Court of Appeal. The appeal court also agreed with the lower court's refusal to stay the proceedings permanently on account of abuse of process.

Among other things, Mahjoub's counsel had claimed the case was gravely tainted by use of hearsay evidence and unsourced intelligence evidence, information derived from torture, breaches of solicitor-client privilege and the interception of privileged phone calls.

At one point, several federal lawyers and assistants were ordered to quit the case because the government inadvertently walked off with Mahjoub's confidential legal files.

In its decision, the appeal court said that "these particular security certificate proceedings can only be seen as fundamentally fair in their execution."

"True, occasionally mistakes and faults happened and often remedies were needed to redress them. But individually or collectively, there is no factual and legal basis upon which the Federal Court could have permanently stayed these proceedings. They properly ran their course to a final decision on the merits."