Agence France-Presse | May 19, 2007

Canada's airlines will have greater leeway to bar passengers who appear to be dangerous under a proposed rule change the Ministry of Transportation announced Saturday. 
The new rule would "strengthen air operators' ability to protect the safety of all passengers and crew by refusing to board those who may represent a threat to that safety," the ministry said in a statement.

"The proposed regulatory amendment to the Canadian Aviation Regulations would deal with passengers whose words or actions could interfere with the safe operation of the aircraft and create an unintended hazard for the aircraft, its crew and its passengers," the statement said.

The rule would create four classes of threats, from inappropriate language to air sabotage. 

Current rules open airlines to lawsuits and place the burden on airlines to justify the refusal of service.