While Canada remains on the outside of ballistic missile defence in North America, it is contributing cash toward the development of a similar, somewhat less sophisticated NATO system in Europe, federal documents reveal.

An issues paper, prepared for Defence Minister Harjit Sajjan in the fall of 2015, shows Canadian officials have participated in discussions at the alliance level about the Europe-based defence system and Canada "contributes financially to elements" of the program.

The initial cost of the missile defence system was pegged at $1.1 billion, but upgrades could add at least another $300 million to the price tag (all figures are Canadian), which is expected to be borne by all 29 NATO members through their quarterly contributions.

The Canadian government will contribute $77.9 million toward alliance operations and an additional $60.1 million to NATO investment programs in the current budget year.

Since the missile money goes into a common fund, National Defence and NATO say they do not have a precise tally of how many Canadian dollars have been allocated to the development of the system, which has limited direct benefit for the Canadian military.

"Canada considers the NATO system to be solely for the protection of NATO European territory, populations and forces," said the documents, obtained by CBC News under access to information legislation.

Can't cherry-pick

In 2005, the Liberal government of former prime minister Paul Martin decided not to participate in a North America-based version of ballistic missile defence — a position upheld in the Trudeau government's recent defence policy.

A spokeswoman for Sajjan tried to reconcile the contradiction of paying to protect Europe from the missiles of rogue states, but not North America.

"It is not inconsistent for an international alliance to have common defence policies while individual nations have their own policies," said Jordan Owens in an email statement.

Canada cannot cherry-pick what the military alliance does with the country's overall contributions, she argued.

"As a committed member of NATO, Canada contributes to the collective defence of our European allies and partners in a variety of ways."

In fact, under the rules of the program, each nation does have a limited say on what aspect of ballistic missile defence will be funded by its dollars.

Canada contributes to the development of the command-and-control system, which links a web of radar installations and anti-missile batteries throughout Europe at sea and ashore.

Harper limited Canada's role

When the former Conservative government signalled its intention to participate in the NATO program in 2010, the idea was to protect alliance troops and installations, but it has been expanded in the years since to defend the entire European continent.

And it was former prime minister Stephen Harper who insisted at the 2010 NATO leaders summit in Lisbon that clauses be added limiting the scope of the program to Europe, says Richard Cohen, who served as an adviser to former defence minister Peter MacKay.

Stephen Harper and Peter MacKay share a laugh during a bilateral meeting in Kiev, Ukraine in 2014. A former Harper adviser says the former Conservative prime minister limited Canada's role in NATO's ballistic missile shield. (Sean Kilpatrick/The Canadian Press)

"I never figured out why he put that language in," Cohen told CBC News. "I could not understand the government's aversion to this. Of course, it's tied to the reluctance of all governments to go into North American [ballistic missile defence]."

He said he doesn't believe Canada's military leadership is keen on any form of a missile shield because it takes money out of the budget for equipment.

"It's only there to defend us if we happen to be on European territory," said Cohen.

"We're contributing all right, but we're not getting a lot back."

Evolving system

In its earlier form, NATO's missile shield may not have caused many waves, but Peggy Mason, of the Ottawa-based Rideau Institute, said Russia has been increasingly vocal in its criticism.

"They're seeing it as a threat to their own security and they're seeing it as potentially part of an offensive capability," said Mason, who served as Canada's disarmament ambassador at the UN.

NATO vehemently denies the system has an offensive capability.

"In arms control terms the system is becoming more and more destabilizing and before Canada contributes to that it seems to me we should have a much more careful discussion within NATO because the system is actually growing."

In a tacit acknowledgement of the criticism and in order to placate Moscow, the Obama administration in 2013 cancelled plans to upgrade the NATO system with faster and more capable missile interceptors.

Cohen says being outside the North American missile shield is becoming increasingly perilous in light of North Korea's recent long-range tests.

Mason dismisses that notion.

"Whatever anyone might say about the leader of North Korea, he's interested in survival and he's interested in regime survival and he seems to have come to the conclusion that in order to avoid being attacked by the United States … you'd better at least have a few nuclear weapons to protect you," she said.

North Korean leader Kim Jong-un watches the test of a new type of anti-aircraft guided weapon system in this undated photo released by North Korea's Korean Central News Agency (KCNA) in May. (KCNA via Reuters)

Mason added that experts believe the U.S. system does not work and will likely come with an enormous cost with no meaningful input for Canada.

Although the recent defence policy closes the door again on a North American missile shield, Owens said the Liberal government is committed to modernizing the North Warning System, a chain of radar stations in Alaska and Northern Canada that has been the eyes and ears of NORAD's air and cruise missile defence for decades.