CBC News has learned the RCMP has disrupted or intervened in 28 instances involving people who fall into its high-risk travel category. That includes people who have returned home after joining a government-designated terrorist group abroad and are intending to travel again, or people who are sympathizers in Canada and are about to travel abroad.

Intervention and disruption is a process the Mounties use as they gather evidence that may lead to future charges. It can include conducting interrogations, talking to family members, surveillance and even referring some cases to Passport Canada to have the suspect's passport revoked.

The 28 cases CBC News has learned about all fall into the high-risk travel group and are being monitored closely by both the RCMP and CSIS.

ISIS is one of several dozen groups considered "listed terrorist entities" in Canada. Other listed groups include al-Qaeda, al Shabab and the Taliban. (Reuters)

If an imminent threat to aviation is detected, a person may be put on Canada's Specified Persons List, otherwise known as the no-fly list.

The government will not confirm the number of Canadians on the no-fly list and will only confirm that "multiple passports" have been revoked under Canada's anti-terrorism laws.

On CBC Radio's The House this week, Immigration Minister Chris Alexander tells host Evan Solomon that the government is looking at revoking the passports of all 80 people who have returned to Canada after working with militant groups abroad.

"It's been done multiple times.... If you've been abroad breaking the law, participating in terrorist acts, those are grounds for revoking the passports," he said.

Few convictions so far

Even with all the interventions and disruptions, there has only been one conviction under the Criminal Code prohibition against attempting to join a foreign group classified as a terrorist organization. There are five cases where someone has been charged with the criminal misuse of passports, according to the RCMP.

Canadians should expect more charges and convictions in the future, according to Alexander.

"The number of people suspected of having been fighting with these groups in Iraq, Syria and elsewhere around the world is 80. That represents a crime under Canadian law. We are determined to investigate each and every one of those cases and prosecute them when the evidence is sufficient to allow that," he said.

Changes to security systems coming

Changes to Canada's security systems are also on the way. Alexander said the government is putting in place an information sharing system to ensure that law enforcement, where they have the authority to do so while conducting an investigation, have access to information about people who have come into or left Canada .

The government is also reviewing security legislation to see whether there are any gaps that hindering security and law enforcement agencies.

"There may be additional gaps in our legislation, in our regulations that could prevent our security and law enforcement agencies from doing everything they need to do inside Canada and outside Canada to track, investigate and prosecute terrorists suspects. So that's being looked at now," Alexander said.

CBC Radio's The House airs Saturdays on CBC Radio One at 9 a.m. and on SiriusXM Ch. 169.