Retired general and senator Romeo Dallaire says Canada should finally embrace ballistic missile defence.

Dallaire tells The Canadian Press that the threat posed by North Korea should itself be cause for Canada to reconsider its decision not to participate in the controversial U.S. missile-shield system.

But he says the technology has also come a long way since Canada said no in 2005.

And Canada's participation would legally obligate the U.S. to shoot down a missile fired at its northern neighbour, Dallaire says, which isn't currently the case.

Prime Minister Justin Trudeau appeared to close the door this week on Canada getting involved in the U.S. system.

However, Dallaire believes the issue will soon resurface in earnest as the U.S. and Canada move to modernize and upgrade the North American Aerospace Defence Command, or Norad.