Zimmerman was not ordered to “stand down” or to stop following Treyvon.
When Zimmerman was asked what he was doing, he replied that he was following Treyvon.
The exact words of the 911 dispatch was “we don’t need you to do that”
That sounds like a suggestion rather than an order.
It wasn't even a 911 dispatch. It was the nonemergency number for the Sandford police. That's clear from the FAQ issued by the City of Sanford, Zimmerman's written statement, and from the charging affidavit by Corey.
Does a dispatcher have the authority to give orders? Nobody ever answers that question, but in any case that was the wimpiest command imaginable if that is what they call it.