The federal government sometimes left people on Canada's no-fly list without lawful justification, according to a recently released report from one of the country's intelligence watchdogs.

The National Security and Intelligence Review Agency (NSIRA) probed whether the Passenger Protect Program, more commonly known as the no-fly list, is working and whether the government treats individuals reasonably and fairly.

"A well-functioning program is crucial for public trust in both national security and individual freedoms," the review agency wrote.

Passenger Protect Program allows the government to bar individuals — Canadians and non-Canadians — believed to be a threat to aviation security from boarding a commercial flight to, from or within the country.