A long time ago – maybe six or seven months – the idea of stripping Canadian citizenship from dual citizens who dabbled in terrorism was considered highly controversial. Civil libertarians, refugee lawyers and thoughtful editorialists warned that such a move would give too many arbitrary powers to the state and violate some of our most fundamental notions of justice. "As Canadians, we make our citizenship feeble and fragile if we let government ministers seize the power to extinguish it," refugee lawyer Lorne Waldman told the Toronto Star.

Well, that was then. Last week the government went further, announcing that it had already begun revoking the passports of would-be jihadis who were planning to fight abroad, and also of people who are already there. These people might not be able to come back – a prospect that might distress their families, but certainly not anybody else. "We need this kind of measure to prevent people from going down this misguided path, and to deter young people from even thinking about it," said Chris Alexander, the Citizenship and Immigration Minister. This time, scarcely anybody raised a peep. It's safe to say that most Canadians overwhelmingly agree with the government.

What happened? The Islamic State. Slaughters of the innocents. Unspeakably barbaric beheading videos. The world changed after 9/11, and then we went back to sleep. Now we're seeing heads on spikes. That's hard to ignore.

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The new campaign to get tough on jihadi tourists is being led by none other than Barack Obama, in concert with the United Nations. On Wednesday, the Security Council unanimously adopted a binding resolution requiring all nations to prevent the recruitment and transport of would-be foreign fighters.

The resolution attracted unusually wide support, because jihadi tourism is a global problem. Terror groups have been a magnet for foreign fighters from some 80 countries. An estimated 3,000 European jihadis are now operating in Syria and Iraq. According to the Canadian government, about 30 Canadians are with extremist groups in Syria. Another 130 are elsewhere, and 80 have come home.

One fear is that foreign fighters might return to carry out terrorist acts back home. In May in Belgium, a gunman who'd spent time in Syria opened fire at the Jewish Museum and killed four people. Last week, Australia rounded up a bunch of people who were alleged to be planning a "demonstration beheading." But Islamic State-style terrorism is primarily an international threat. As in Afghanistan in the early days, the fighters gain experience and connections they will keep for life and deploy elsewhere. "Even if America with the support of other countries destroys [Islamic State] tomorrow, and even if they dislodge them from their territory tomorrow, you still have 12-15,000 people that have been there, that have made contacts there, that go somewhere," terrorism expert Peter Neumann told ThinkProgress.

Some countries haven't waited for the UN. Australia's government wants to make it a crime for Australians to travel to "no-go zones." Britain's David Cameron has called for the government to rescind the passports of would-be jihadis and revoke the citizenship of those already fighting. He wants mandatory government re-education programs for everyone suspected of being radicalized. "It absolutely sticks in the craw that someone can go from this country to Syria, declare jihad, make all sorts of plans to start doing us damage and then contemplate returning to Britain having declared their allegiance to another state," he said. None of the other major parties have objected.

Justin Trudeau, the Liberal Leader, has said he opposes the Conservatives' new measures, and that homegrown terrorists should be dealt with through the criminal justice system. "I think that a lot of Canadians, including very conservative Canadians, should be worried about the state willing to, and taking the power to, arbitrarily remove citizenship from people," he said. "That's a slippery slope that I don't think we want to go on."

But Mr. Trudeau – who is now out of step with the rest of the world – will not be eager to raise the subject again. After all, Prime Minister Stephen Harper has allied himself not only with Britain and Australia, but with Barack Obama and the UN.

It's a very serious matter for governments to revoke the passports of their citizens, restrict their freedom and deprive them of their citizenship. And people who warn that states might abuse their new powers are right. Without vigilance, they probably will. Finding the balance between national security and personal liberty is always tricky. But our first obligation is to protect ourselves – and the world – from bad Canadians. The virus of murderous fanaticism hasn't gone away. And it will be around for a long time to come.