HUNTINGTON BEACH, Calif. —  Convicted sex offenders are barred from surfing at the famous pier in this Orange County city.

In nearby Dana Point, they are prohibited from casting a fishing line in the harbor.

And if they wander into a public park in Mission Viejo, they could be shipped back to jail for six months, following the city council’s vote this year to ban them from a host of places where children congregate.

“We need to protect our kids,” the Orange County district attorney, Tony Rackauckas, had told the Mission Viejo City Council. “The danger is very real.”

Orange County finds itself at the epicenter of a new wave of laws restricting the movement of sex offenders. The county government and a dozen cities here have banned sex offenders from even setting foot in public parks, on beaches and at harbors, rendering almost half the parks in Orange County closed to them. Ten more cities are considering similar legislation.

And Orange County is far from alone. In recent years, communities around the country have gone beyond regulating where sex offenders can live and begun banning them outright from a growing list of public places.

From North Carolina to Washington state, communities have designated swimming pools, parks, and school bus stops as “child safety zones,” off limits to some sex offenders. They are barred from libraries in half a dozen Massachusetts cities and from all public facilities in tiny Huachuca City, Ariz.

“Child safety zones are being passed more and more at the city and county level,” said Elizabeth Jeglic, a professor at John Jay College of Criminal Justice. “It’s becoming more and more restrictive. They’re not only limiting where sex offenders can live, but they’re limiting their movement as well.”

The proliferation of such restrictions reflects the continued concerns of parents and lawmakers about potential recidivism among sex offenders. But the implementation of these restrictions has increasingly raised questions about their effectiveness, as well as their fairness.

Opponents have dismissed “child safety zones” as unenforceable, saying they are designed to make politicians look tough on crime and drive sex offenders from the area, not make children safer.

“These are cheap laws that can be passed to make people feel good,” said Charles P. Ewing, author of “Justice Perverted: Sex Offense Law, Psychology, and Public Policy.”

Irene Pai, a lawyer with the Orange County public defender’s office, said “child safety zones” give parents a false sense of security, punishing many offenders who are not dangerous without actually stopping predators from entering parks.

Pai said she had a stack of cases involving people who were arrested for urinating in public in the 1970s and pleaded guilty to indecent exposure without realizing they would have to register as sex offenders.

“The very notion that a park ordinance could in any way protect children, more than an attentive caregiver’s presence or any other way we protect our children, is absurd,” she said.

Greg Bird was convicted of indecent exposure in 2001. Since then, however, Bird said he has gotten married and turned his life around.

But he now pauses at the idea of having children of his own, because he knows he could not even take them to the park to play catch.

“Sometimes I wonder, is there any compassion?” Bird said. “I know I don’t deserve compassion. I broke the law. I get that. But these laws set people up to fail more.”

In some cities, law enforcement has done very little to enforce child safety zones. In Albuquerque, where some sex offenders have been banned from libraries since 2008, with some exceptions, the police have never even issued a trespass notice, a prerequisite to an arrest.

Thus far, the park bans here have led to just three convictions across the entire county.

Still, Rackauckas said he was satisfied that the laws were serving as a deterrent.

“We’re not going to know how many kids were not molested or groomed for later sexual contact as a result of this law,” he said.

At La Bonita Park in La Habra, parents largely supported the ban.

“I feel better bringing my 2-year-old grandson to the park now,” said Barbara Bellen, 51.

And, once one community has enacted “child safety zones,” they often spread quickly to nearby towns, as municipal governments fear becoming local havens for sex offenders.

In Lake County, Fla., earlier this year, county commissioners — surrounded by communities with tough laws targeting sex offenders — responded with some of the most dramatic restrictions anywhere, including a law prohibiting sex offenders from coming within 300 feet of a park, school or playground.

“We wanted to assure our residents that if they took their kids to the playground, they wouldn’t have to worry about someone in the parking lot across the street watching them,” said Leslie Campione, a county commissioner.

Even so, in Lake County a lower-level offender like Bird would be allowed visit the park as often as he liked, because the ban applies only to those whose crimes were against minors.

Not so in Orange County, where the prohibitions are among the most severe yet, aimed at all sorts of offenders.

Sex offenders here can apply to the Orange County sheriff’s department to be allowed into a county park. So far, 15 applications have been submitted; all but one has been denied.

One applicant requested access to Dana Point Harbor to continue working as a commercial fisherman. Another was a locksmith who did work at businesses at the harbor and said he had a clean record during 28 years living in the area. A third wanted to attend a memorial service for his Alcoholics Anonymous sponsor, who had recently died.

All three requests were turned down.

Since Orange County set up its “child safety zones,” 12 cities in the county, two other counties in California and two cities in Arizona have all done the same.

With the exception of Irvine, Calif., all of them have applied the ban to all registered sex offenders.

Joe Carchio, a city councilman in Huntington Beach, where a park ban went into effect in December, said he feels bad for lower-level offenders whose convictions many years ago prevent them from bringing their children to Little League. Still, he wishes he could have made the restrictions even broader.

“In a lot of ways, it is a feel good law; it makes people feel safe,” Carchio said. “You make choices in this world, and I guess the choice that individual made is one that is going to follow him for the rest of his life.”