Say you slept with your girlfriend when you were a senior in high school and she was a freshman. That’s enough to get you labeled a sex offender in some states.

Or say you streaked across the football stadium buck naked in college, or urinated outside when you were drunk, or clicked on the photo of a naked 17-year-old.

Strange as it may seem, all these “crimes” have the same punishment in the end: After serving time, doing probation and/or paying a fine, the people who committed them get on the sex-offender registry.

And now, if the US House of Representatives approves an amended bill that the Senate passed just before Christmas, those citizens will have the words “Sex Offender” branded on their passport.

Kind of makes it hard to travel.

The motivation behind the International Megan’s Law is ostensibly to prevent sex tourism and trafficking. The problem is that the sex-offender label in no way reflects a person’s risk of re-offending — or even whether they ever committed what I’d consider an actual sex crime. (I don’t think of streakers as sex criminals. Do you?)

The general belief is that sex offenders have one of the highest recidivism rates around — that they get out of prison only to offend again. Surprisingly, the opposite is true. A report by the Bureau of Justice followed almost 10,000 sex offenders after their release from prison. It found that 5.3 percent were rearrested for a sex crime within three years. That means 95 percent of those labeled “sex offender” didn’t re-offend — a recidivism rate lower than for any other crime except murder.

There are almost 850,000 Americans on the Sex Offender Registry, up from 750,000 just a few years ago.

About a quarter of them got on the list when they were juveniles themselves, because young people have sex with other young people. Labeling all of these offenders’ passports means branding hundreds of thousands of citizens who won’t commit another sex crime.

That’s overkill.

It also means branding as sex offenders a whole swath of citizens whose offenses aren’t even considered crimes in the countries they’re trying to visit. For instance, I have a friend who had sex, once, with a 14-year-old when he was 19. If he had done this in Austria, Germany, Portugal or Italy, it wouldn’t have been a criminal act at all. The age of consent there is 14.

But here in America he went to prison — for nine years. He spent his 20s in a cell for one act of consensual sex between two teens, and now that he’s out, he remains on the Sex Offender Registry for life. What a country!

If my friend’s passport is stamped with “Sex Offender,” any country he approaches will assume he’s a monster trying to get in.

Oddly enough, that country won’t be alerted if a visitor has served time for, say, mugging old ladies. No one’s American passport will be stamped with “Drug Dealer” or “Drunk Driver” or even “First-Degree Murderer Who Used a Pitchfork”!

The only people our government intends to brand are the people who committed a sex crime, did their time and are now free. They’re American citizens like the rest of us . . . except for the scarlet “SO.”

If there was any proof that branding the passports would actually cut down on sex trafficking, a heinous crime that makes my heart ache, maybe a rational argument could be made for it. But there isn’t.

“There are already federal laws in place requiring registered sex offenders to notify the Department of Justice if they are leaving the country,” says Emily Horowitz, a professor of sociology at St. Francis College in Brooklyn and author of “Protecting Our Kids? How Sex Offender Laws Are Failing Us.”

She adds: “Why make another expensive and pointless law aimed at a group already marginalized?”

Why? Because it’s hard to stick up for the rights of anyone labeled a sex offender, even if they’ve done their time and are highly unlikely to offend again.

And it’s easy to pretend you care about making kids safer, even if the evidence shows you’re doing nothing constructive at all.

Lenore Skenazy is author of the book “Free-Range Kids” and founder of the blog of the same name, and a contributor at Reason.com.