She should have a right to speak, though as the Supreme Court has noted (to the country's detriment), money is speech these days, and so letting UCB bill her or her sponsors for the exorbitant costs of security to ensure a peaceable assembly also seems reasonable.  (However likely it is that Ms Coulter wanted no such peaceable assembly and was specifically hoping for the free press she could wallow in on Fox etc after some sort of Milo Riot Redux.)