You are not allowed to put tables on the sidewalk without a permit. Some places have a succah in the back on their own private property, I dont think you need a permit for that.
And for those who think the permit is silly, what if a wind comes and blows down the succah on the sidewalk and someone gets hurt or property gets damaged. I know of a case where the succah blew down and damaged someones car so its not so far fetched