In my last two columns, I discussed the cases of young people who were placed on sex-offender registries because their sexual partners were below the age of consent. For the rest of their lives, any neighbor or employer who looks them up on the Web will be led to believe they are pedophiles.

This raises many questions, among them: What is the right age of consent?

The legal age is different everywhere. In Yemen, it's 9, although you have to be married. In Mexico, you can legally have sex as early as 12. In the United States, the age varies by state, ranging from 16 to 18.

For "20/20" I spoke to an 18-year-old boy who had sexual relations with a girl four years younger. Isn't that taking advantage of a 14-year-old? I asked.

"I wouldn't think so. I thought I was really gonna have a relationship."

What if she were 13?

"I really can't answer that question ... because she wasn't."

What if she were 12?

"Oh, heck no. There's a point where you draw the line somewhere."

But where? The law is at odds with what goes on in real life. The Centers for Disease Control reports that a quarter of America's teens say they had sex before they were 16. Since no state's age of consent is lower, millions of Americans must be breaking the law.

Some groups, like the Family Research Council, say the laws should be stricter.

"We oppose efforts to lower [the age of consent]," Peter Sprigg, its vice president for policy, told me.

But 17-year-olds are still going to have sex.

"Well, they are. But I think it's a legitimate goal of public policy to discourage that."

Making it illegal discourages it?

"There will be some deterrent effect presumably. That's what all of our laws do."

Family counselor Dr. Marty Klein disagrees.

"The idea that we criminalize 14-year-olds' having oral sex or sexual intercourse with 16-year-olds, that's a horrible solution to a subtle and complex issue."

Klein calls this criminalization of sexual activity America's War on Sex.

"Telling a kid just say no, and expecting them to not have sex, that's like telling somebody who's depressed, have a nice day, and expecting that to lift their depression."

Some states created exemptions to their statutory rape laws for kids who are close in age. They're called "Romeo and Juliet" exemptions because Romeo and Juliet were close in age. But I bet the legislators would be surprised to learn that Shakespeare's Juliet was only 13.

Klein says, "We trust 15-year-olds to make decisions all the time. We give them access to credit cards. We let 16- and 17-year-olds drive cars. The idea that somebody who's behind the wheel of a car can't make good sexual decisions, I think, is more about our anxiety about sex than it is about any clear thinking about 17-year-olds."

But the Family Research Council's Sprigg will have none of this. "The focus should be on telling teens that sex should be saved for marriage. The benefits of waiting are enormous."

If they're too young, why did God make them biologically ready? I asked him.

"Well, in some ancient cultures, it would have been perfectly appropriate for young people to marry and start a family as soon as their bodies were biologically ready for reproduction. But we live in a very different culture, and young people today need more time before marriage, but they don't need sex before marriage."

Whatever the law says, there's no proof that age-of-consent laws deter sex before marriage. Many kids don't even know what the age of consent is.

Something is very wrong when young people, doing what hundreds of thousands of other kids do, are condemned for life on sex registries next to rapists and real pedophiles. There's no justice in that.

John Stossel is an award-winning news correspondent and author of Myths, Lies, and Downright Stupidity: Get Out the Shovel--Why Everything You Know is Wrong.

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