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The reason true democracy actors must always do it "by the book", is the problem of the lowered bar.
If you infringe the rules for what is seen a good reason at a time (the generic example is "there is a bomb in the town, the security services detain one of the terrorists. Is it ok to torture him to learn where is the bomb planted ?"), then there is a temptation to go further the next time a less dangerous situation arise. This slow eroding of the safeguards and individual liberties is what we have witnessed not only during the Bush era, but it started even before mid-70's, especially in Europa. This lesson was learned the hard way first by my compatriots in the algerian war, and the last repercussions of that only happened in the 90's (starting by calling it a war and not evenements).
Btw, this tricky question is a problem only for democracies. The others wont have any guilt to get an answer, and you wont have any problem to imagine which it is. But when democracies do like the autocrats, they just lose a bit of their "mandate of heaven" as chineses would call that.
That dont mean that "No" is the only answer, but that it is a very serious question and that the consequenses must be checked and accounted for. The main problem with the Bush era is the lack of accounting which resulted in angering even closest allies.