"Newps" wrote in message news:nohob.50763$ao4.131616@attbi_s51...
We were always told that if you don't want someone in the airspace you
tell them to remain outside the class D/C airspace.

That wasn't universally the case. Some of the ARSA's (this predates the lettered namespace)
were specifically using the "I can't hear you" approach in lieu of explicitly denying service.