Someone with a bomb in a backpack is hardly likely to agree to a search.
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OK, so I'm a terrorist bomber, carrying a bomb in a backback. Nice to know that if I don't agree to a search I can carry on my way, unmolested.
"Nice to know that if I don't agree to a search I can carry on my way, unmolested."
No you can't carry on the way unmolested. But that's rather academic as the method of 'not agreeing' would tend to be rather, erm, explosive.