TULSA, Oklahoma - Many people were surprised Sunday's kidnapping suspect was caught in part because a store clerk saw the words sex offender stamped on Michael Slatton's driver's license.

The clerk says those words caught his attention because Slatton was acting strange and buying coloring books and crayons.

Oklahoma passed the law seven years ago and it requires habitual or aggravated sex offenders to have it printed on their driver's license, those are considered to be the worst of the worst on the registry.

The people who have to have the words sex offender stamped on their driver's license are people convicted of first and second degree rape, sodomy, rape by instrumentation, sexual battery, sexual abuse of a child, incest, lewd acts or proposals to a child or someone who has committed two or more sex crimes that require registration.

Slatton had sex offender on his license, because he sexually battered a 58-year-old woman in her Claremore apartment in 2005.

The clerk let police know about the man because of the license and his strange behavior. It wasn't until later that he heard the Amber Alert.

That information was key to Slatton's arrest and recovering the eight-year-old girl who'd been kidnapped.

"That was a huge help," said Sergeant John Adams of the Tulsa Police Department. "That was our first bit of information."

The law says sex offenders must renew their license every year instead of every four.

Those against the law say it punishes sex offenders by making them pay more money, plus, embarrasses offenders who are doing simple things like buying groceries.

They argue it's like a scarlet letter that identifies the sex offender to the world, even though they already paid for their crime. Plus, they say these special driver's licenses don't make children or society safer.

Police say the Supreme Court says sex offender registration laws, including these licenses, don't punish, they only regulate.

"If you're a registered sex offender, your information is already out there for the public to see," Adams said. "Only people you should see your driver's license are merchants, if you're cashing a check and law enforcement. You don't pin your ID to your jacket as you're walking around."

Oklahoma has around 7,000 registered sex offenders. The state couldn't tell me how many of them are required to have the special driver's licenses, but, Tulsa estimates about 25 percent of its registered offenders are habitual or aggravated.

If that holds true for the state, it would put the number around 1,800.