The decision this week of an Islamic court in Nigeria to acquit a woman who faced death by stoning for adultery is a triumph for sanity. If Nigeria, a huge nation encompassing various faiths, had upheld the sentence, it would have given such a punishment legitimacy in other Islamic nations and regions. But the verdict leaves many troubling questions. As the legal codes of more places reflect the influence of Koranic principles, known as Shariah, they must do so in ways that do not violate international law and the rights of their citizens.

When Amina Lawal's daughter was born two years after she was divorced, Ms. Lawal was arrested for adultery and sentenced to death. This week the court overturned her conviction on technicalities and did not address the justice of stoning, an exceptionally cruel sentence considered to be torture. Ms. Lawal's lawyers argued that it was discriminatory that the man she identified as her sexual partner won acquittal by swearing that he had not committed adultery — a defense not available to her. The court rejected this argument.

Nigeria is sharply divided between a Muslim north and a Christian south. To defuse religious and ethnic tensions, President Olusegun Obasanjo, a Christian, permitted the northern states to begin using Shariah in 1999. He had apparently not counted on the worldwide embarrassment that cases like Ms. Lawal's have brought Nigeria. The court that ruled this week may have been under instruction to block the stoning, but in a way that did not anger Muslims.

When it was introduced 1,400 years ago, much of Shariah was more progressive than the legal cultures it replaced. Parts of it — letting women inherit property and keep their property after they marry — still are. Yet extreme versions are spreading, especially where literacy is low. They are often less reflective of the Koran than of local cultures.

Inspired by a growing group of fundamentalists, people accept Shariah as a defense against what they see as the encroaching decadence of the west. In Nigeria and other nations with large Muslim populations, governments resort to Shariah to placate these extremists. But in doing so without regard for their own constitutions and human rights, these highly political accords mean that a nation's lowliest citizens are the ones who suffer.