Canadians who travel overseas to join extremist groups can expect to have their passports revoked, the government is warning.

Citizenship and Immigration Minister Chris Alexander said Saturday that Ottawa has begun revoking travel documents for those who travel to places such as Iraq and Syria to fight with the Islamic State and other militants groups.

鈥淚f we have evidence 鈥 and I mean substantive, incontrovertible evidence 鈥 that someone has left Canada with the intention of committing what would be an indictable offence here, including terrorism, then we can revoke, suspend or invalidate their passport,鈥 Alexander told 麻豆影视.

The minister said the Islamic State is not just a problem in the Middle East, but a global threat.

鈥淕iven the barbaric nature of the groups operating now in Syria and Iraq, and their unscrupulous tactics, we need this kind of measure to prevent people from going down this misguided path, and to deter young people from even thinking about it,鈥 he said.

The measures are 鈥渟erious, strong legal safeguards,鈥 that Alexander said will 鈥渙nly ever going to apply, we think, to a small group of people.鈥

Alexander said the power to revoke travel documents was already established under the Canadian Passport Order, and that it had been used in the past. He said 鈥渕ultiple people鈥 have already had their passports revoked in light of recent situations, but declined provide specific numbers.

Citizenship and immigration lawyer Joel Sandaluk said while it鈥檚 true the government is within its rights to revoke passports, the apparent secrecy surrounding the decisions is troubling.

鈥淭he thing that鈥檚 curious about this is, it鈥檚 not exactly all that clear on what information the government is basing these revocations,鈥 he said. 鈥淭he government is asking us to place an extraordinary amount of faith in their ability to operate.鈥

Without any insight into how the government is collecting its information, it鈥檚 possible decisions are being made based on suspicions and imperfect information, Sandaluk told CTV鈥檚 News Channel.

鈥淎nd the suggestion that they鈥檙e doing this within the full rigor of the law isn鈥檛 really entirely clear to me, because it seems to be a process that is shrouded in mystery,鈥 he said.

More than 130 Canadians are thought to be fighting with extremist groups abroad, with several dozen estimated to be in Syria and Iraq. In a new Islamic State recruitment video, an alleged jihadist with an apparent North American accent speaks on camera.

Though the propaganda video has yet to be authenticated, it could be the first of its kind, says an expert on terrorism.

鈥淚f this is a North American, this would be quite extraordinary because it's the first time that a North American ISIS fighter has committed a war crime on-camera,鈥 said analyst Paul Cruickshank.

Alexander said in addition to having their passports revoked, dual nationals who commit acts of terrorism could also have their Canadian citizenship revoked, according to new powers gained by the government this summer.

鈥淭his is not going to come to any surprise to those fighting with terrorist groups,鈥 he said. 鈥淭hey know they鈥檙e committing a crime already, in the eyes of Canada.鈥

He said taking away their passport would make it more difficult for them to operate.

鈥淎nd it will ensure that the good name of Canada, which is associated with this passport, is not associated with the menace of terrorism.鈥

With files from CTV鈥檚 Laurie Graham