ORLANDO, Fla. — The American Civil Liberties Union and two co-plaintiffs are suing Polk County, alleging that requirements for exhibiting in its “free-speech zone” are unconstitutional.

The zone was created after a church group erected a manger scene outside a county building in Bartow last December without permission. Within several days, other items were placed on the lawn, including a sign celebrating “Festivus,” the holiday made famous by the television comedy “Seinfeld.”

Polk officials then determined that potential exhibitors had to be approved by the county attorney, have $500,000 in liability insurance and agree not to hold the county liable.

The ACLU argues the rules are unconstitutionally exclusionary in a lawsuit filed Dec. 9 in federal court in Tampa.

“The problem is really very simple. In creating essentially a public forum, Polk County opened that area for free speech for all of its residents,” said Mike Pheneger, chairman of the Greater Tampa chapter of the ACLU of Florida. “They’ve given it to you, but then they’ve taken it away from a segment of the citizenry.”

Polk officials say the rules were necessary to protect the county from liability, and they say courts have been inconsistent in setting precedents for how much insurance is acceptable.

“Unfortunately, the case law has just not clear on this subject,” County Attorney Joe Jarret said. “If it were, we’d have a better benchmark from which to work.”

Co-plaintiffs include the Humanist Association of West Central Florida and Stella Darby, whose display near the manger last year read “Zarathustra Zoroaster,” in honor of an ancient Persian religious figure.

The ACLU applied last month to build a “Bill of Rights” display at the free-speech zone but refused to pay the liability insurance. Pheneger said insurance would have ranged from $368 to $510 per day.

“At that point, you’d have to say the county has put a pretty hefty price tag on the freedom of speech,” he said.