Yes, it is possible to identify whether the user allowed Core Location or not, although I want to re-iterate that terminating your app at that point is discouraged (as Chris Gummer pointed out).
The CLLocationManagerDelegate protocol has a method locationManager:didFailWithError: that will be called with an error code of kCLErrorDenied
if the user does not allow Core Location to be used. You can watch for that error and have your app act accordingly.
If the user does allow Core Location to be used, locationManager:didUpdateToLocation:fromLocation: will sent to your CLLocationManagerDelegate with the new location.