The case of Paul Wolfowitz presents an opportunity to take a harder look at nepotism in international institutions and set new rules to determine when close relatives may legitimately work together and when they may not.

Current and past U.N. secretaries-general have had to deal with this issue. So have some at the World Bank — and not just its president. The U.N. Development Program has had it crop up in almost every office it runs around the world. So let’s do something about it. Let’s make some sensible rules.

Mr. Wolfowitz could be forced to resign as head of the World Bank, as his role in facilitating a pay raise for his girlfriend, Shaha Riza, appears to have undermined his campaign to end international welfare as we know it.

The story seemed simple. He preached against giving money to corrupt tin-pot dictators who use funds meant for the poor to enrich themselves and their cronies. How credible can that campaign be if you help your girlfriend to a sizable raise? I’m shocked, shocked to hear there is nepotism at the World Bank.

Well, maybe not all that shocked. Until 2005, the wife of the bank’s managing director, Shengman Zhang of China, worked directly under him. The bank also employed a brother of its chief economist and senior vice president, Nicholas Stern of Britain, violating its own rule against employing siblings.

Initially, Mr. Wolfowitz attempted to avoid any such violations. “In order to avoid any conflict of interest, real or apparent, and consistent with Staff Rule 4.01, I recuse myself from any personnel decisions or actions with respect to Ms. Shaha Riza,” he wrote to the board of the bank’s ethics committee in 2005. But the committee, headed by Ad Melkert of the Netherlands, advised him to take charge of his girlfriend’s case.

Mr. Melkert has since moved on to the UNDP, an agency that habitually hires office employees recommended by local governments. In many cases, the United Nations ends up being represented locally by friends and family of the country’s dictator.

During his visit to Syria this week, Secretary-General Ban should be on guard. A local UNDP officer, Khaled Mouallem, might relay internal U.N.communications to his father, Foreign Minister Walid Mouallem, at the dinner table. (The daughter of Walid Mouallem’s predecessor, Farouk Shara, also worked for the UNDP during her father’s tenure.)

What else should Mr. Ban watch out for? Someday, an Indian national who works for the United Nations Children’s Fund in Nairobi, Siddharth Chatterjee, may want to be promoted to a top UNICEF position, known as country resident, in an African country. Such a promotion would require the approval of the U.N. secretary-general, who happens to be his father-in-law. Mr. Chatterjee’s wife, Hyun-hee, is Mr. Ban’s daughter, and she also works at UNICEF’s Nairobi office.

Family problems, of course, dogged Mr. Ban’s predecessor, Kofi Annan, after reports emerged that a company where his son worked received a fat contract from the U.N. oil-for-food program. However, the case of Mr. Annan and his son, Kojo, is fundamentally different from that of Mr. Ban and his daughter and son-in-law and that of Mr. Wolfowitz and Ms. Riza in at least one crucial aspect.

Like Ms. Riza, who served at the World Bank before her boyfriend became its president, Ms. Ban and her husband worked for UNICEF before Mr. Ban became secretary-general. Unlike Kojo Annan, who stood to benefit from his father’s status, Ms. Riza and the Chatterjee family stood to lose out as their relatives became head of the institutions they worked for.

To avoid such a loss, Ms. Riza received compensation when she was forced to move out of the World Bank, where she was overdue for a promotion. She then became a target of members of the so-called international community and of an industry that has not been all that aghast at nepotism in the past.

Mr. Wolfowitz exposed himself to allegations of hypocrisy when he put fighting corruption at the top of his agenda — in an institution that had previously been too eager to dole out funds, regardless of how recipients used them. The lesson is clear: At international institutions, you fight corruption at your own peril.