At least in the US, ATC, dispatch, and even an "Airline Representative" (=Management) can declare an emergency for an aircraft.
For example, here's a
page with a transcript and a recording of a controller doing just that.
As for management-declared emergencies, I haven't been able to find any recordings, but that's no doubt due to the cabin crew's ability to keep the Champagne at the proper temperature. There's still some debate about whether improperly served nuts constitute an emergency.
Of course, I didn't say that Schiphol tower declared an emergency; just that he treated it "as an emergency", handing off to a discrete channel and stopping all arrivals and departures.