No they shouldn't.
There's always a big argument on this subject, about whether it's possible to to get useful information with torture.
But I would tell you that this is beside the point. Why? For a couple reasons.
For one thing, regardless of whether it's possible to get useful information, it's almost certainly possible to get completely wrong information, from people who will say practically anything to get out of the torture. Which is what most people ultimately do. This leads to tortured people handing over all the names of other people they can think of, for example, regardless of whether the other people are guilty of anything or not. The people on the new list are brought in and tortured, and guess what? They all produce even more names. In practically no time at all you'll find yourself torturing absolutely huge numbers of people, essentially at random, and producing huge amounts of absolutely useless "intelligence," mainly consisting of all these random people saying whatever the hell they think will get the torturers to stop.
And for the other thing, institutionalized torture is, primarily, I think, a tool favored by repressed sadists. People who would like to do evil things to others, that is, but who lack the personal courage to do so unless they have official permission. And so they put themselves in a position where they have a mandate from the government to do it. These folks will carry out the program indefinitely, according to the pattern I laid out in the previous paragraph, without ever once questioning whether the information they're obtaining is actually any good. Because they don't really care about the information. They just want to torture people.
Now, I do happen to think that it is in fact possible to get useful information out of people with torture, in case you wanted to know. But that does not mean I think institutionalized torture is necessary, or that it should be allowed. As an institution, it is a net liability, for the reasons I've already stated.
If however, you happen to be some kind of police officer, or spy, or what the hell ever, and if you think you can really save the nation by torturing some guy or other, and if you really believe this is the only way to go? I think you should be willing to go ahead and do it, even though it's against the law. And you should be willing to take the legal penalty for having done so.
After all, you're saving the nation, right? If you really do save the nation, surely the nation will go easy on you, recognzing the great, heroic deed you've accomplished.
And if it turns out you didn't actually save the nation? Or that there was never any threat in the first place? Well that works too. Because then you'll be in prison where you belong anyway.
See, this what I like to call, standing on your principles. If you really believe in this crap, put your money where your mouth is. Stop demanding the nation pin a damn badge on your chest and hand you an official permission slip and full immunity from prosecution first.