"We have pretty stringent policies related to filming in the library," Cleary said. "The logic behind the policy, first and foremost, is about the protection of our patrons."
Cleary said videographers must seek permission from library officials as well as a city permit to film indoors. Members of the news media do not need a permit, she added, but they still must receive permission from library officials.
Glendale library regulations also state permission will be granted only if filming "will not disrupt library business," and if the film session is 30 minutes or less. Library users and staff may also not be filmed.
"Anybody who uses our auditorium needs to seek our permission to have cameras in the room," Cleary said. "That had not happened."
She added that given the history between the two sides, "It had potential to be disruptive."
Cleary acknowledged that the advent of smart phones, YouTube and other changes has blurred once-clear lines regarding the library's filming regulations, and that some amendments could be needed.
"Our policy is several years old," said Cleary. "I do think it merits some review, but at this point we are following the policy we have in place."
Musurlian has posted several videos critical of Gatto on YouTube. A video of Saturday's event shows Gatto adviser Larry Kaplan shouting at Musurlian and Glendale officers telling Musurlian to leave.
On Tuesday, Gatto said Musurlian is a "stalker" who has intimidated members of his staff and distorted the truth in his videos.
"I could say 'fussbudget' and he'd end up editing it into an expletive," said Gatto.
He also accused Musurlian of working for Sunder Ramani, the Republican Gatto defeated in the special June election. Gatto and Ramani will face off again in November for the full two-year Assembly term.
Ramani campaign manager, Bo Patatian, said that while he knows Musurlian, "There is absolutely no relationship between him and the Ramani campaign."
"I have not collaborated with any campaign at all, and am not paid by anybody," said Musurlian.
For his part, Musurlian accused the Gatto camp of working with police and library staff to find a reason to boot him from the event.
"They were just trying to get me out of there," he said.