Apperantly he didn't slap the official. As you can see from the photo above McGregor actually punched him and according to reports, very long suspension is on the horizon for mcgregor.
You can watch the incident here.
McGregor committed 7 different crimes in the Bellator incident.
1-) Jumped into the cage as a viewer.
2-) Verbally assaulted the referee and pushed him.
3-) Then he ran afterwards the ref and violently shoved the referee from behind while the ref was checking on the knocked out fighter.
4-) Pushed and ran over the knocked out fighter while he was screaming at Goddard.
5-) McGregor was escorted out but after awhile he came back to the cage and furiously tried to reach the referee Goddard again.
6-) He left the cage again only to jump back onto it afterwards.
7-) This time he punched the official Mike Johnson in the photo above that was trying to restrain him from entering into the cage again. Johnson allegedly went to police afterwards.