The State Fair is on pace to draw more than a million people to the fairgrounds in Raleigh this year, but residents who are on the state’s sex offender registry risk arrest if they are among them.

A new law that went into effect Sept. 1 bans the more than 17,000 registered sex offenders at the 163-year-old event. Supporters of the law say it protects children attending the fair from harm.

“It’s a place where there’s a lot of children, a lot of children running around, without direct parental supervision, who may be at risk if predators are around,” said Sen. Buck Newton, a Johnston County Republican who sponsored the bill. “It made sense to me. I don’t remember anyone voting against it.”

But the head of a new group that advocates on behalf of the state’s registered sex offenders says the law deprives an entire class of people of their civil rights. Robin Vanderwall, who co-founded the North Carolina chapter of Reform Sex Offender Laws, said the group intends to file a lawsuit in federal court before year’s end seeking to have the new law declared unconstitutional.

The bill was introduced at the urging of state Agriculture Commissioner Steve Troxler, who earlier this year said the state needs tougher laws to ban sex offenders from the fair. During the 2015 State Fair, Wake County sheriff’s deputies arrested four registered sex offenders at the fair, including someone who was initially charged with flying a drone over the event and a convicted child molester who was charged with posing as a state inspector to get into an area reserved for children’s rides.

Only one of the four was wearing an ankle bracelet that some sexual offenders are required to wear, said Wake County Sheriff Donnie Harrison. The bracelets are equipped with global positioning systems that enable probation and parole officials to monitor the wearer’s movements.

Harrison said his office is working with probation and post-supervision officers across the state to identify sex offenders who may try enter the fair. If a sex offender wearing an ankle bracelet gets within a certain distance of the event, someone will call the sheriff’s office, Harrison said.

“If the person is inside the fairgrounds, we will pass that individual’s picture out to our officers,” he said. “It’s a good game plan, and it’s evidently working. We haven’t had any arrests.”

State Fair spokesman Brian Long said the Department of Agriculture and Consumer Services supported the bill and monitored its progress in the General Assembly, where it passed unanimously in both chambers and was signed by Gov. Pat McCrory on July 21.

“We wanted to make it clear because of the number of children who come here,” Long said. “It’s a child-oriented, family event. We wanted to keep it that way.”

But Vanderwall said it’s unfair to violate the civil rights of registered sex offenders who have served their criminal sentences and fulfilled all of their probation or post-release supervision obligations. He likened the new law to old Jim Crow laws.

“For the first time since 1891, thousands of North Carolina citizens and taxpayers are legally prohibited from attending the state fair,” Vanderwall said in a press release. “African Americans were officially ‘uninvited’ to attend in 1891 and remained ostracized from fair activities until the creation of so-called ‘Colored days’ in the early Twentieth Century.”

Vanderwall said that of the state’s more than 17,000 registered sex offenders, only 28 have been determined by the courts to be sexually violent predators. Vanderwall said the designation has to be declared by a judge who has reviewed expert testimony that shows an individual’s sexual predilections are untreatable and the person is mentally ill and likely to repeat the offense.

“I’m sure Donnie Harrison can flag 28 people to keep them out of the State Fair,” he said. “That’s easier than banning 17,000 people.”

Newton said state legislators who supported the law had “difficult decisions to make.”

“We have to respect the rights of people with a history [of sex offenses], against the legitimate work of trying to protect children against those who might commit future acts,” he said.