I don't know much about non-EG Civics, but on EGs there's a plastic plug on the clutch pedal that pushes against a switch located above the pedal (sorta under the dash). When the cruise is set and working, and you push on the clutch pedal (even just a little), the switch lets out and the cruise is switched off until you push the resume button (and the clutch pedal is not being depressed).

Easier to show, harder to describe... I don't have any pics of this switch. But they may not have that on a 2001.