The national union that represents border guards is reigniting the debate that these officers should be allowed to arm themselves at international airports after an incident in Calgary led a dozen of them to refuse to work over claims of unsafe conditions.

Jean-Pierre Fortin, national president of the Customs and Immigration Union, said at least one officer with the Canada Border Services Agency working at the Calgary International Airport received a threat this week, though it's unclear who made it.

CBSA officers — who are generally required to store their firearms at international airports — later requested armed security.

But for 10 hours Thursday, no other force, including Calgary police, was available to provide an armed presence, Fortin said.

Officers requested to arm themselves

Border guards asked CBSA management whether they could arm themselves, but their request was denied.

In response, a dozen or more officers refused to work, invoking their rights as federal employees to do so, if they believe that they or the public is in danger.

"It was well justified," said Fortin.

CBSA, however, does not believe agents at the airport were ever in any danger.

"We have no evidence of a credible threat," said spokeswoman Lisa White, adding the incident caused no disruptions for travellers at the airport.

White said the CBSA reassigned the concerned airport agents to other roles and called in other employees to fill their positions.

Agents continued to refuse work as of Friday

According to the union, four or five agents continued to refuse to work in their roles at the airport as of Friday afternoon.

The incident is now under investigation by federal health and safety officers.

Fortin said the federal government has long argued that border agents working at international airports don't need to be armed because of their proximity to local police forces, but he believes the incident in Calgary is "proving them wrong."

"Police presence is not there at all times, 24 hours, so that's a problem for our officers," he said, adding armed CBSA officers would be better situated to provide security during any potential attacks.

White declined to comment on the call for armed agents while the investigation into the incident continues.