One sexual predator, when interviewed by the FBI, described his experience with foreign child prostitutes this way: “It’s like being a star. They want to try my food. They want to see what clothes I wear. They want to watch my television.” Such “stars” are the global consumers of innocence, exercising a particularly brutal form of power over the poorest, most vulnerable children on Earth.

About 25% of sex tourists targeting children are from America, traveling to Latin America, Asia, and Africa in search of abomination on the modified American plan.

Another predator told the FBI he shouldn’t be prosecuted because the girls he used were professionals. In his case, they ranged between the ages of 13 and 15. Other transactions involve boys younger than 10.

These “professionals” are often recruited by kidnapping or deception. With two or three “customers” a night, they suffer lasting physical damage and become particularly susceptible to venereal disease. They often end their lives as social outcasts, addicted to drugs and alcohol.

The language of commerce — “professionals” serving “customers” — is misapplied to violent child abuse.

Until recently, according to Joe Mettimano of World Vision, child sex tourism resulted in “less than a handful of arrests, and fewer convictions.” Nations such as Thailand, Cambodia, Costa Rica, Mexico, and Brazil were reluctant to admit and confront an embarrassing problem — a kind of national venereal disease.

And these crimes are inherently difficult to prosecute here at home, depending on the testimony of frightened children and evidence gathered in foreign countries.

But since 2003, Mr. Mettimano says, there has been “real progress” in ending this impunity — more than 50 child sex tourism indictments in America, resulting in over 35 convictions. He praises the Department of Justice and U.S. Immigration and Customs Enforcement for their aggressiveness. And he credits Thailand, Cambodia, and Costa Rica for “at least making an effort” to oppose child prostitution.

Child sex tourism is not only a story of horrors; it provides an example of how an effective social movement can develop in a matter of years. And this achievement offers some lessons.

First, political leadership is crucial. “President Bush has provided good leadership,” Mr. Mettimano says, “both on human trafficking and sex tourism.” He increased spending on programs to fight the trade, issued an executive order requiring departments to confront the issue, and shamed nations that tolerate child prostitution in his 2003 address to the United Nations General Assembly. In any eventual assessment of Mr. Bush’s foreign policy idealism, his personal engagement on issues such as HIV/ AIDS, human trafficking, and child sex tourism will need to be taken into account.

Second, legal changes can matter greatly. Previous to congressional passage of the Protect Act of 2003, prosecutors had to prove that sex tourists went abroad with the intent of molesting children — something almost impossible to demonstrate. The Protect Act shifted the burden, making predators liable for the act itself. Penalties were doubled to 30 years in prison from 15. And with convictions more likely, law enforcement officials and prosecutors have been more motivated.

Third, religious activism makes a difference on a global scale. For several years conservative Christians have been at the forefront of the campaign against modern slavery, working closely with traditionally liberal human rights groups.

Support for human trafficking legislation in 2000 included the unlikely pair of Chuck Colson and Gloria Steinem. This kind of alliance is potent because it communicates a broad national commitment.

These efforts are not unprecedented, and neither is the issue of child prostitution. A House of Lords report in Victorian England found that “juvenile prostitution from an almost incredibly early age is increasing to an appalling extent.” In 1885, a crusading newspaper editor of the Pall Mall Gazette set out to demonstrate that children could be readily bought and sold in London. He managed to purchase a 13-year-old girl named Elizabeth Armstrong from her mother for 3 pounds sterling on delivery and 2 pounds more when her virginity was confirmed.

The story about Armstrong — headlined “The maiden tribute of modern Babylon” — sold a million newspapers in a week and ignited a national scandal. The Salvation Army opened houses of refuge for prostitutes, and sent out Midnight Rescue Brigades to counsel young streetwalkers. And the British Parliament quickly increased the age of consent to 16 from 13.

Yet it remains possible in our world to purchase 13-year-olds. Some Americans do it all the time. And it still deserves our outrage and activism.