You can unregister any delegate without getting an error, whether it is named or not or registered or not. (Why, I don't know, possibly for efficiency reasons or simply because it is not required by the C# standard).

By holding a reference to the delegate, you can successfully unregister it:

using UnityEngine;

public class LogItInAwake : MonoBehaviour
{    
    delegate void EventHandler();
    EventHandler LogIt;

    void Awake()
    {
        EventHandler x = () => Debug.Log("It");

        LogIt += x;
        LogIt -= x;

        LogIt();
    }    
}

Some more info:

• http://stackoverflow.com/questions/183367
• http://stackoverflow.com/questions/292820/how-to-correctly-unregister-an-event-handler