This week, with little ceremony and no debate, Canada's Prime Minister ordered the military into action on a foreign shore. We're not at war: The six CF-18 jets now stationed in Romania are, in the words of Defence Minister Rob Nicholson, "sending out a message to Russia" about its aggressive stance toward Ukraine.

This North Atlantic Treaty Organization gesture, accompanied with escalating sanctions, is sensible and measured, and probably has the support of most Canadians. But not all – there have been well-argued cases against it from across the political spectrum.

Historian Michael Bliss argued in this newspaper that the action is a dangerous incursion into what he sees as Russia's sphere of influence. Columnist Thomas Walkom suggested in the Toronto Star that he sees this as a regional issue and none of our business. There are probably plenty of Canadians, and MPs, who share those views, and who would raise them in a parliamentary debate.

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But there wasn't a debate, and there won't be one. The Prime Minister has no need to ask Parliament, or anyone else, for permission to make use of the military, the intelligence services or any other federal force outside Canada's borders. Even if he wanted to declare all-out war on Russia and all of its allies, Stephen Harper could do so on his own (after seeking the advice of his cabinet), through the Royal Prerogative, without any discussion in a democratic assembly and without any review by the Supreme Court.

This is because Canada wasn't designed to have a role in the world. University of Toronto political scholar Irvin Studin points out in The Strategic Constitution: Understanding Canadian Power in the World, his new book examining the Constitution's international-affairs provisions, that Canada is unique in that it doesn't really have any.

The Constitution Act's only substantial description of any foreign-affairs role is the line in its preamble which states that Canada's purpose is to "promote the Interests of the British Empire." We were created to be a colony, and we never changed that – the Charter of Rights established Canadians as individual citizens rather than royal subjects, but was mute on our country's actions in the world.

You might think that this colonial mandate would prevent the government of Canada from doing much on the international stage. In fact, it means the opposite. We've ignored that provision for most of the past 150 years (you can do that with a preamble), leading to what Dr. Studin calls a "remarkable paradox": Because international affairs is barely mentioned in the Constitution, absolutely anything done abroad, or done to Canadians because of perceived international threats, is relegated more or less to the prime minister's personal executive discretion under either the Royal Prerogative or the "Peace, order and good government" provision.

This has led to all sorts of consequent paradoxes. For example, Canada may go to war strictly on the whim of a sitting prime minister (since this act involves the military, which is strictly a federal prerogative), but if we ever found ourselves defeated in a war, a surrender would require the consent of all 10 provinces (because we'd be surrendering various things that are strictly under provincial jurisdiction).

This means that a prime minister can, if convinced that Canada is threatened from abroad, use the Emergencies Act to order "everything from prohibitions on travel to requisition or seizure of property, control of specified industries, and removal from Canada of non-citizens."

Not only that, but a prime minister could, if he felt Canada faced a "real or apprehended war, invasion or insurrection" legally invoke both the Charter's "notwithstanding" clause (which allows basic rights to be suspended) and Section 4(2) of the Constitution (which allows Canadian elections to be suspended indefinitely in wartime unless opposed by a vote of more than one third of MPs). This, Mr. Studin notes, "would be tantamount to a fairly potent cocktail of executive override of most of the Charter's key rights provisions."

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Dr. Studin is rather obsessively interested in Canada's ability to "project strategic power in the world" – that is, he sees the lack of constitutional restrictions as a source of flexibility and strength. But this also means that our governments can put unlimited numbers of Canadian lives at risk overseas without directly asking the people through their Parliament.

These governments have been lucky: Bosnia, Kosovo, Libya and Afghanistan (at first, at least) were widely supported missions, and we wisely stayed out of Iraq, so most Canadians haven't noticed how undemocratic these missions are.

In 1939, 1994 and 2006, Parliament was given symbolic debates on military deployment, generally after the decision had been made. The next time around, a principled prime minister ought to let Parliament speak first, and decisively.