I don't know how things are done where you live, but here the general consensus is that if you don't want people trick or treating at your home you turn off your porch light. Occasionally you may forget about turning off the porch light and have children knock on your door. In that case a simple "I'm sorry I'm all out of candy" or "We don't participate in Halloween" will suffice. Heck, even a nice little note on the door would be good. Which leads me to wonder about this house.
Honestly, I couldn't make this crap up if I tried. I mean really, are trick or treaters that bad that you have to rope off your driveway and front porch? Perhaps you had a bad experience with Halloween as a child? And yes, I would totally be lying if I told you that I have not thought about dressing up and ringing their doorbell just to see what happens.