WASHINGTON (Reuters) - Political activist Andy Cilek arrived at his local polling site in Eden Prairie, Minnesota, on Election Day in 2010 wearing a T-shirt touting the conservative Tea Party movement with the words “Don’t Tread on Me” as well as a button stating, “Please I.D. Me.”

FILE PHOTO: Voters wait in line at a polling station in Greenville, South Carolina, February 20, 2016. REUTERS/Rainier Ehrhardt/File Photo

His attire was enough to get him stopped in his tracks by a poll worker because Minnesota law forbids voters from donning political badges, buttons or other insignia inside polling places during elections. Cilek eventually was permitted to vote, but the confrontation became a key part of a legal challenge that reaches the U.S. Supreme Court on Wednesday.

The nine justices will hear arguments over whether the state law violates the U.S. Constitution’s First Amendment guarantee of free speech. Cilek is being represented by a prominent conservative legal advocacy group, but also has the backing of the American Civil Liberties Union.

At least nine other states -- Delaware, Kansas, Montana, New Jersey, New York, Tennessee, Texas, Vermont and South Carolina -- have similar restrictions on political apparel at polling places, according to the plaintiffs.

Minnesota defends its law as necessary to keep order at polling places at a time of intense U.S. political polarization.

Political messages on apparel “could give rise to verbal disputes or even physical altercations,” a court filing by Minnesota Secretary of State Steve Simon and other officials said, citing fights at polling locations in Florida and Michigan on Election Day 2016.

“Tensions may well be running high, particularly when the election has been a contentious one,” they added.

The Minnesota Voters Alliance, a St. Paul-based conservative group headed by Cilek that brought the case with the support of the Pacific Legal Foundation, is appealing a lower court ruling that upheld the state law. The challengers said merely wearing something political at a polling station is a peaceful act.

In Minnesota, election officials have interpreted the law as barring campaign literature and material from groups with political views such as the Tea Party movement or the liberal MoveOn.org. Violators are asked to cover up or remove offending items. If they do not, the may still vote, but their names are to be taken down for possible prosecution. The state said it has no record of prosecutions under the law.

THIRD TIME’S A CHARM

Cilek said he was twice turned away from his polling site on Election Day 2010 because the head election judge disapproved of his attire, including the button that alluded to voter-identification laws backed by many Republicans.

On his third try, Cilek said, he was allowed to vote.

“I was just thinking that they’re hell bent on not letting me vote,” Cilek said in an interview. “I was just kind of shocked by the whole deal.”

Cilek, a 54-year-old former U.S. marine, said the genesis of the lawsuit was a perception that election officials were targeting groups they did not like.

“It’s an absurd policy that you’re going to allow election judges to be the arbiters of free speech,” Cilek said.

In a brief filed supporting Cilek’s group, the ACLU warned against allowing poll workers discretion to decide what is impermissibly political.

“A phrase that one person may consider to be innocuous or nonpolitical -- like ‘#MeToo’ -- may appear to another to be an overtly political statement,” the ACLU said, referring to a movement encouraging women to share their experiences of abuse.

Minnesota said the law is applied neutrally and helps prevent confusion or intimidation during voting. The law is similar to one in Tennessee that the Supreme Court upheld in 1992 barring vote solicitation and the display or distribution of campaign materials within 100 feet (30 meters) of a polling place, the state said.

In rulings in 2013 and 2017, the St. Louis-based 8th U.S. Circuit Court of Appeals upheld the Minnesota restrictions, suggesting the law helps maintain “peace, order and decorum” at polling sites.

“On the one hand, the Supreme Court has recognized that areas immediately around polling places can be zones free of politics,” said Richard Hasen, a University of California, Irvine professor specializing in election law. “On other hand, Minnesota’s law appears quite broad.”

Michael Dimino, a constitutional and election law professor at Widener University Commonwealth Law School in Pennsylvania, said Minnesota is going to have to show that the ban is the least restrictive means of solving the problem it is meant to address.

“Speculative arguments based on what could happen are the kinds of arguments that governments have used for decades to justify overly broad crackdowns on speech,” Dimino said.