Well, if this lady is to be believed, apparently the only way to keep Arbery under control was to point a shotgun at him. They really are pushing that citizens arrest angle, but I really, really don't see it working. The prosecution has driven that one into the ground pretty well.
The fact that the McMichaels -- both with a law enforcement background -- shouted at Arbery several times, but never said "You're under arrest!" or "We're making a citizen's arrest!" should be enough to eliminate that claim.