ST. PETERSBURG, Fla. - The questions have been asked by many this week: If there are safety concerns regarding white supremacist Richard Spencer speaking on campus, then why allow it? And why are taxpayers paying for event security?

Since speaking during a Confederate monument rally in Charlottesville, Virginia, where a protester was killed, the University of Florida, Texas A&M University, Louisiana State University and Michigan State University blocked his speaking engagements, citing safety concerns.

Spencer threatened to sue.

Now, UF believes it legally has to let him speak.

University President Kent Fuchs cited the First Amendment and freedom of speech - regardless of how divisive it is.

"UF is required by law to allow Mr. Spencer to speak on our campus and that we are not allowed to bill him for the full cost of keeping our campus safe," he said.

Security costs are expected to reach $500,000. Fuchs said more than 500 law enforcement officers will be on hand during Spencer's speech.

Watch: White supremacist Richard Spencer to speak at University of Florida campus

A Supreme Court decision prohibits a speaker paying the full security cost, for doing so could prevent the speech from happening.

No state entity, including a public university, can favor or deny a speaker based on what they have to say due to the First Amendment, constitutional law expert Louis Virelli said.

"The university is not permitted to deny him access to an otherwise public forum because to do so would be to choose one kind of speech over another or to be acting specifically against a particular message...which the First Amendment protects us against," he said.

Spencer's speaking event is scheduled for 2:30 p.m. to 4:30 p.m. Thursday at the Phillips Center for the Performing Arts at 3201 Hull Road in Gainesville, Florida.

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