Divorce proceedings bring out the worst in people. When Abdul Rahman tried to get custody of his daughters in Kabul, Afghanistan, his wife's family told the court that he was unfit to care for his children because he had converted from Islam to Christianity some 16 years ago. A zealous prosecutor, hearing of the case, charged Mr. Rahman with apostasy, a crime punishable by death under some interpretations of Islamic law. If Mr. Rahman does not repudiate Christianity, the judge in the case has said, he will get the death penalty.

Mr. Rahman's case is a discouraging illustration of the uneasy balance between the democratic norms Afghanistan's Constitution enshrines and the conservative Islamic values its judiciary upholds. On the one hand, the Afghan Constitution states that "followers of other religions are free to exercise their faith and perform their religious rites within the limits of the provisions of the law," and it requires the state to adhere to the Universal Declaration of Human Rights, which clearly protects freedom of conscience and the right to change one's religion.

On the other hand, the Constitution also says that no law can be "contrary to the beliefs and provisions of Islam," and it gives judges broad power to interpret and apply Islamic law. Several schools of Islam do indeed prescribe the ultimate punishment for those who abandon the faith. And so Mr. Rahman's case may well come down to the interpretive leanings of the court.

Moderate Islamic jurists in some countries have attempted to balance or reconcile these often-conflicting interests. In Egypt, for instance, the Islamic Research Center decreed that although apostasy may be a crime, the time period for redemption is limitless - in other words, it is up to the individual, not the state, to adhere to divine will. The former chief justice of Pakistan, which has explicit anti-blasphemy laws, has written that the death penalty for apostasy is not required by the Koran and conflicts with other Islamic values.

Afghanistan's post-Taliban judiciary, however, has shown a propensity to use Islam as a political weapon. The country's chief justice, Fazil Hadi Shinwari, is a hard-line conservative associated with the Islamist parties of Abdul Rasul Sayyaf and Burhanuddin Rabbani. He has used the court as a bully-pulpit, issuing fatwas on a variety of issues outside his jurisdiction.

For instance, under Justice Shinwari's leadership the Supreme Court has variously attempted to ban co-education; tried to eliminate a rival to President Hamid Karzai from the 2004 elections; and jailed newspaper editors, all in the name of Islam.

In other words, the court has overstepped its bounds and contributed to the radicalization of Afghan politics in the process. To further his aims, Justice Shinwari has packed the lower courts with judges who have Islamic educations but no foundation in Afghan law or experience in the judiciary.

President Karzai has a unique opportunity to change this. Under the Constitution, Mr. Karzai must appoint a new Supreme Court this month, and he sent his slate of nine justices to Parliament for approval last week. Although the current chief justice has retained his position, there are some very promising choices among the eight other justices. They include known moderates, like the former chairman of the Judicial Reform Commission, Bahauddin Baha, and the deputy minister of justice, Qasim Hashimzai, who led a major corruption investigation involving members of President Karzai's cabinet.

These appointments mark President Karzai's first opportunity to compose Afghanistan's Supreme Court under a fully constitutional government. They are of momentous importance to the country's stabilization and the consolidation of its nascent democracy.

By creating a competent, professional and moderate judiciary, President Karzai will help to establish the rule of law. If, however, the court remains in the thrall of ideology and factionalism, Afghanistan's experiment in democracy will be compromised.

But the new judges will be powerless to reform the system unless they are given the political support and resources to do so. International involvement in Afghanistan's justice sector since 2001 has been inadequate. Both the Afghan government and its donors need a strategic vision for the judiciary's future and the political focus to make it a reality.

The new judiciary will need support to review the qualifications of the lower court judges, facilities to train new judges and functioning courthouses in the provinces. It will need to be able to share information, laws and legal decisions among officials throughout the country and to pay judges a living wage.

We must do more than simply react loudly to the most extreme cases, like that of Mr. Rahman. Instead, we must partner with the Afghans and other democratic governments in the Islamic world as they struggle to promote modernity and the rule of law. This means working with judicial systems on less controversial, bread-and-butter issues like criminal law and property disputes.

We have seen throughout the world, and in our own history, that competent and independent judges will stand up for the rule of law even when their decisions indict the powerful and defend the unpopular. Mr. Rahman's case should remind us of how important it is to help Afghanistan develop such judges if we want its democracy to succeed.