My new book Uncertain Shield: The U.S. Intelligence System in the Throes of Reform is about the reorganization of national-security intelligence that Congress decreed (unwisely in my opinion) in the Intelligence Reform and Terrorism Prevention Act of 2004. It is not a book about civil liberties. I have written such a book—Not a Suicide Pact: The Constitution in a Time of National Security—which will be published in September. The only discussion of civil liberties in Uncertain Shield comes in a chapter in which I discuss the case for creating a domestic intelligence agency, on the model of Britain’s MI5 or the Canadian Security Intelligence Service, the latter of which figured prominently in the recent detection of the Toronto terrorism plot. A domestic intelligence agency or Security Service (the official name of MI5) is an agency separate from the national police (in the United States, the FBI) that has no arrest powers but uses surveillance and other intelligence methods to detect and foil terrorist and other threats to national security. The FBI has done badly as a counterterrorist organization for reasons I explain in my book, and the urgency of establishing a Security Service is underscored by the London transit bombings of July 2005 and now the luckily foiled Toronto plot. For, we too have a large Muslim minority (much larger in absolute terms than Canada’s), and these episodes show that we too must be concerned about the danger of terrorist attacks mounted from within the country by citizens and other legal residents. We must also be concerned about attacks from Canada, which has a Muslim minority of 600,000 who, like other Canadians, live within a short distance of our long and largely unguarded northern border.