FINANCIALLY TROUBLED Europe has plenty to worry about. Yet some in the Old World have decided this is a good time to pick a fight with Islam and Judaism over a ritual that both have practiced for many centuries: circumcision of young males.

In June, a state-level appeals court in Cologne, Germany, released a ruling making it a crime to circumcise a male younger than 18, except to treat an ailment. The case involved a 4-year-old Muslim, circumcised by a Muslim doctor at his parents’ request. The court said parental autonomy and religious freedom must yield to the child’s right of “physical integrity.” The ruling did not set a national precedent, but it put an accepted practice under a legal cloud — to the point where the German Medical Association advised doctors to stop elective circumcisions for the time being.

To her credit, Chancellor Angela Merkel criticized the ruling, and last week the German parliament passed a resolution calling for legislation that would clarify the law to permit Jewish and Muslim practices. But at least one German opinion poll suggests that the public opposes such a law.

Meanwhile, the Cologne case reverberates. On Tuesday, the governor of the Austrian state of Vorarlberg ordered public hospitals to cease religious circumcisions in view of the ruling. In Zurich, the children’s hospital has suspended circumcisions until at least next month, pending a review of what a spokesman called “medical and ethical issues” raised by the Cologne court.

The court’s case against circumcision mixes extreme and insensitive secularism with unstated but radical mistrust of parents. Though aimed at religiously motivated circumcisions, the ruling would also bar those carried out for hygienic reasons. “The experts confirm that — at least in central Europe — there is no need to carry out circumcision for preventive health care,” the court explains. This strangely provincial formulation wildly oversimplifies global evidence on the risks and benefits of neonatal circumcision: While hardly a must, it can help prevent certain diseases, almost always without serious complications, such that a perfectly reasonable parent could conclude that the procedure is beneficial, not a criminal assault, as the Cologne court would have it.

The United States has its own “intactivists,” who succeeded in getting a referendum banning under-18 circumcisions onto the San Francisco ballot in 2011 — until a judge ruled it out for technical reasons. Wherever they might occur, circumcision bans that disrespect religious traditions, or parents’ ability to weigh medical evidence, would be profoundly misguided.

As it happens, circumcision will be much discussed at this week’s International AIDS Conference in Washington, because the procedure can help prevent the spread of HIV. Studies in Africa show that it reduces the risk of heterosexual transmission by up to 60 percent.

The World Health Organization and UNAIDS have recommended more voluntary circumcisions in 14 African countries with high rates of HIV infection. Achieving 80 percent compliance among 15- to 49-year-olds could avert 3.4 million new infections. This is an ambitious goal. We hope the conflict and uncertainty being sown in Europe do not make it even harder to achieve.