There are moments when Stephen Harper is utterly unfathomable.

The latest came last week, in an interview with the CBC. Almost casually, the prime minister said he would reinstate emergency anti-terrorism powers - allowing judges to compel witnesses to testify in secret hearings and police to jail terrorism suspects without warrant for up to three days.

These measures had originally been created in the frightened and feverish atmosphere following the 9/11 terrorist attacks, but even then they were controversial. The first had a whiff of the Star Chamber.

The second eroded the ancient protection of habeas corpus. Supporters argued, rightly, that they didn't curtail civil liberties all that severely, but that argument missed the real danger.

As history has shown so often, extraordinary times pass but the extraordinary powers they spawn do not. We become accustomed to them, even forgetting why they were created, and they become ordinary powers. They are used more liberally, even in ways not contemplated at all when they were passed. And they spread to new legislation.

After all, if the powers are ordinary and accepted, why not use them elsewhere?

"Time will pass, as will this crisis. But the law will live on," I wrote at the time. "We will get used to 'preventive arrests,' forced assistance in investigations, sweeping wiretaps, and the rest. The extraordinary will become ordinary. The cancer will metastasize."

That's a hell of a danger. But then, so is terrorism. So what's the answer? Are these powers truly necessary?

At the time, many informed people thought so. Many others disagreed. But nobody really knew the answer. We were all groping in the dark of an uncertain, unprecedented time.

So a compromise was reached: The new measures would be passed but they would contain a "sunset" clause that would cause them to lapse after five years unless Parliament passed them again. It was an elegant solution that took both dangers seriously.

And it worked. Much to the surprise of many - including me - the powers were not abused. Indeed, they were not used at all. Even once.

That's pretty compelling evidence that the powers were not necessary. And so, quite appropriately, the opposition parties united to stop the Conservative government from renewing them in 2007, the sunset clause kicked in, and the extraordinary powers expired along with the extraordinary time that created them.

If that were the end of the story it would be a textbook example of a sensible and successful legislative response to a difficult problem.

But then Stephen Harper did the unfathomable.

"We think these measures are necessary. We think they're useful," he told the CBC. "And as you know ... they're applied rarely, but there are times when they're needed."

Unless the prime minister has a dictionary that defines "rarely" to include "never," that statement is false.

And why does the prime minister feel the powers are "necessary"? I would like to think his conclusion is based on something more than his nagging fear of the "Islamicists" under the bed. So let's be charitable and assume that security officials told him so.

Did it occur to the prime minister that security officials constantly seek expanded powers? It's in their job description. It's what they do.

Did he push back? Did he demand evidence? Did he ask the officials to explain how on Earth powers not used in the many years they were in force, and not missed in the years they weren't, can be described as "necessary"?

Maybe he did. And maybe those security officials had a good answer based on all that super-secret information they have. Let's be very charitable and assume so.

Then the obvious question is what will the prime minister do to prevent these extraordinary powers from becoming a metastasizing cancer - spreading into organized crime legislation, for example - and eating away at civil liberty? Will the new legislation have a sunset clause like the original legislation?

Stephen Harper hasn't answered that question. But in an interview with CTV, Public Safety Minister Vic Toews gave a vague and evasive answer that made him sound very much like a politician who is not interested in a sunset clause and even less interested in explaining why not.

So extraordinary powers created in an extraordinary time will be restored long after the extraordinary time has passed - even though the powers were irrelevant and unnecessary when they were available and irrelevant and unnecessary when not. And there will be no mechanism to ensure they do not outlive the concern that created them, are not abused, and do not become a metastasizing cancer.

And this will be done by a prime minister who claims to so cherish civil liberty that he considered the long-form form census a violation of freedom so outrageous it had to be stamped out no matter what the cost to social science and sound policy.

Like I said, unfathomable.