Refusing to remove a surgical mask was enough to get a young man arrested at the right-meets-left protest at UC Berkeley on Thursday.

The encounter that led to the arrest — witnessed by a Chronicle reporter —began when another protester arrived at Sproul Plaza shortly after 11 a.m. with a sign that said, “The issue is not free speech, the issue is fascism.”

A small group of university police officers surrounded that man, Raphael Kadaris of the Refuse Fascism group, and told him that his sign violated a campus ordinance against carrying signs larger than 30 inches by 30 inches.

Kadaris, who handed the sign to a bystander, was given a warning.

But the second man, wearing a surgical mask, refused to remove it, identify himself or submit to a photograph.

“I feel like I’m being criminalized,” he said.

He told police he was wearing the mask because of a sore throat and that he had left his wallet and identification at home.

“I plead the fifth,” the masked man told police.

“That’s not applicable here,” the unidentified officer replied.

“Why is that not applicable?” said the masked man.

“We are not in court,” another officer replied.

Police arrested the man, who then took off his mask, cuffed him in plastic restraints and led him away.

A UC Berkeley police spokesman said the man was arrested for obstructing officers, wearing a mask to evade police and giving false identification.

Police were out in force, trying to stem violence in the wake of the cancellation of a speech by conservative commentator Ann Coulter.

At the entrance to campus, authorities distributed leaflets saying that the following items were prohibited because they could be used as weapons: bicycle locks, frozen fruit, balls, laser pointers, plastic water bottles, skateboards and balloons.

Sarah Ravani is a San Francisco Chronicle staff writer. Email: sravani@sfchronicle.com Twitter: @SarRavani