Giddens said he tried to prevent the group from entering, as the campground was managed by Tararua District council and all entrants had to have a vaccine passport.
"If you don't have a passport you can't come in, and the council have been very, very strict on that," Giddens said.
"I told them 'no one can come in here' and then [a protester] went over to the gates, propped them open, and all of a sudden people started streaming in."
Giddens said they broke into one of the toilets and physically threatened him, and he called the police.
"I closed the toilets and all of the offices, because there's big signs everywhere saying you can't enter unless you have a vaccine.
"Then they all came at me and demanded I open the toilets.
"I stood my ground but I got overwhelmed."
A spokesperson from Tararua District Council confirmed vaccine passports were required at all council campgrounds, but said they would not be able to provide any more information as the events at Woodville were a police matter.