... “It’s a battle that’s really just begun,” said Daniel Pipes, who directs a conservative research group, the Middle East Forum, and helped lead the charge against Ms. Almontaser and the school.

In the aftermath of Sept. 11, critics of radical Islam focused largely on terrorism, scrutinizing Muslim-American charities or asserting links between Muslim organizations and violent groups like Hamas. But as the authorities have stepped up the war on terror, those critics have shifted their gaze to a new frontier, what they describe as law-abiding Muslim-Americans who are imposing their religious values in the public domain.

Mr. Pipes and others reel off a list of examples: Muslim cabdrivers in Minneapolis who have refused to take passengers carrying liquor; municipal pools and a gym at Harvard that have adopted female-only hours to accommodate Muslim women; candidates for office who are suspected of supporting political Islam; and banks that are offering financial products compliant with sharia, the Islamic code of law.

The danger, Mr. Pipes says, is that the United States stands to become another England or France, a place where Muslims are balkanized and ultimately threaten to impose sharia.

“It is hard to see how violence, how terrorism will lead to the implementation of sharia,” Mr. Pipes said. “It is much easier to see how, working through the system — the school system, the media, the religious organizations, the government, businesses and the like — you can promote radical Islam.”

Mr. Pipes refers to this new enemy as the “lawful Islamists.”...