I always figured that Starfleet was in no hurry to prosecute Kirk, which is why they were waiting patiently for Kirk and his crew to turn themselves in eventually,
instead of demanding their immediate extradition from Vulcan. Nobody really wanted to throw the book at the legendary crew that saved Earth from V'Ger and brought Spock back to life.
And after Kirk and Co. saved Earth again
, from the whale probe, I figure Starfleet was sincerely grateful, not pissed-off.