He did? When?At the beginning of the episode, Fox says he is there to essentially force a treaty port on the Eminians.
http://www.chakoteya.net/StarTrek/23.htm
KIRK: Code seven-ten means under no circumstances are we to approach that planet. No circumstances what so ever.
FOX: You will disregard that signal, Captain.
KIRK: Mister Fox, it is their planet.
FOX: Captain, in the past twenty years, thousands of lives have been lost in this quadrant. Lives that could have been saved if the Federation had a treaty port here. We mean to have that port and I'm here to get it.
KIRK: By disregarding code seven-ten, you might well involve us in an interplanetary war.
FOX: I'm quite prepared to take that risk.
KIRK: You are. I'm thinking about this ship, my crew.
FOX: I have my orders, Captain, and now you have yours. You will proceed on course. Achieve orbit status and just leave the rest to me. You're well aware that my mission gives me the power of command. I now exercise it. You will proceed on course. That's a direct order.
(He leaves.)
and a bit later:
SPOCK: We know very little about them. Their civilisation is advanced. They've had space flight for several centuries, but they've never ventured beyond their own solar system. When first contacted more than fifty years ago, Eminiar Seven was at war with its nearest neighbour.
KIRK: Anything else?
SPOCK: The Earth expedition making the report failed to return from its mission. The USS Valiant. Listed as missing in space.
FOX: Kirk, what's this about you going down alone?
KIRK: Not alone. I'm taking some security people with me.
FOX: It is my prerogative.
KIRK: I can't risk beaming you down there until I know what kind of reception you're going to receive. Your safety is my responsibility. Those are my orders, sir. Mister Spock.
and still later:
UHURA: A channel is open, Mister Ambassador. You will be speaking to Anan Seven, head of the High Council of the Eminian Union.
FOX: Mister Anan, this is Robert Fox
[Council Room]
FOX [OC]: Special Ambassador for the United Federation of Planets.
ANAN: A great honour, Mister Ambassador.
[Bridge]
FOX: We have approached you openly
[Council Room]
FOX [OC]: With the intent of establishing formal and friendly relations between our peoples, but now,
[Bridge]
FOX: For some reason, you have attacked us, and apparently you're holding several special representatives of our Federation.
[Council Room]
ANAN: A mistake, Mister Ambassador. We are at war.
[Bridge]
ANAN [OC]: An error in our sensors indicated that your ship was about to attack us.
[Council Room]
ANAN: I'm giving orders that our attack be stopped.
[Bridge]
ANAN [OC]: Now, as to your representatives, you have my sacred word as an Eminian that they are alive and well.
FOX: Thank you. I thought perhaps it was all a mistake.
DEPAUL: Mister Scott, disruptor beams are no longer hitting us.
SCOTT: Maintain status, Mister DePaul.
ANAN [OC]: We are most anxious to establish relations with you, Mister Fox.
Fox doesn't appear to be using much force towards Anemiar VII in any of his exchanges.
Just because Fox says he "means to get it" - it doesn't necessarily imply the use of force to make them comply.