"Listen man, we're just going to run a few tests so that I can establish that you're safe to drive. It won't take too long, and you'll be on your way."
Enter, the Drug Recognition Expert. Blow zero? Yeah, doesn't matter.
For further Google fun, look up the 600+ sober DUI arrests in Tennessee.
BREAK BREAK: Just to pull this discussion back on subject. On the side of the road, about the time when the cop starts with the small-talk questions (which are not small talk), I'm limiting my answers, and I will quickly establish that I don't consent to searches or roadside tests.
On the jetbridge is another story. The rules of evidence are different, and I'm more concerned at that moment with my fitness to fly and further employment, in that proximal priority.