Is it constitutional to ban sex offenders from public libraries?

The (challenging?) legal question in the title of this post is prompted by this local story out of Tennessee, which is headlined "Knox bans registered sex offenders from county libraries."  Here are the details:

People listed on the Tennessee Sex Offender Registry are banned from visiting county libraries under an executive order issued Monday by Knox County Mayor Tim Burchett.

He said they can still use the county library system's online services and have a proxy check out and return materials on their behalf. But, they face arrest if caught inside the buildings.  "I just don't want them anywhere around our kids," Burchett said.  "The ultimate decision is how we pursue it.  I want to get out in front of this. There's no need to toil around with it.  I don't want them anywhere around our kids."

The administration said the library system, which has 19 locations, is the first of the state's big four metropolitan library systems to put such a policy in place.  The county, Burchett said, is taking advantage of a state law that went into effect July 1 that gives public library directors the authority "to reasonably restrict the access of any person listed on the sexual offender registry."

Officials will compare a list of registered offenders to its 150,000 active cardholders and then mail them notices, advising them of the change.  State law says that a sex offender who enters a library five days after the notice is mailed can be prosecuted for criminal trespass.  In addition, the county also will post notices on the entrances to all its public library buildings.

Listed offenders on the state's registry include those convicted of sex crimes against children, rape, statutory rape, attempted rape, sexual battery, criminal attempt to commit statutory rape and solicitation to commit aggravated prostitution.  "People will say they've paid their debts to society, but they've given some of those kids a life sentence," Burchett said.  "(Some of the) kids have been abused and they carry it with them for the rest of their lives.  And I don't want to give (the offenders) a chance to be anywhere near them again."

Knox County Sheriff Jimmy "J.J." Jones agreed, saying he was pleased with the new policy. "I applaud the state of Tennessee for putting tougher regulations on these dirt bags who prey on our children," he said.   Officials say they can't recall an incident at the library that involved a sex offender, but communications manager Michael Grider said the Knoxville Police Department is investigating a complaint made roughly a month to six weeks ago....

Sixth Judicial District Public Defender Mark Stephens said Monday he doesn't question the county's purpose of ensuring public safety, but he questioned whether the move was constitutional.  "A regulation like this proposes too broad a ban to include people who impose no threat to library goers," he said.  "A ban like this would have to be so narrowly tailored to avoid infringing on the rights of those people who don't present a risk, and the Knox County proposed ban doesn't meet that test."

Stephens said a New Mexico district court recently ruled that a similar ban in Albuquerque was unconstitutional.  Additionally, he said courts have held that public libraries are limited public forums, which means the First Amendment protects peoples' rights to use them.

When asked whether the county's plan unfairly punished those whose crimes were not child-related, Burchett said:  "Sometimes people plead down to lesser offenses.  My main concern is protecting innocent people, and all we're doing is enforcing state law and going after it very aggressively.  I don't know how you'd differentiate.  The state can work that out."