Is sump pump supposed to discharge back onto property or onto the street curb?
You cannot make a case for yourself saying just because others do it you should be able to (just try that with a cop when getting pulled over for speeding) 

What I have done in the past is to run the drain line to the curb and fill the last foot with gravel, when there is enough water it flows through the gravel and over the curb direct draining was not allowed, but this was legal, a big nosed neighbor trued to cause problems and called the city after I did this I did not get cited but several others on the block did, now every one has the same setup, makes no sense to me but if it flows out of the ground and over the curb it was legal in that city.