The dangers of this ruling come on multiple levels. The most obvious danger is that a federal judge can now destroy an intelligence program. If a group is able to file a suit in front of a friendly judge, then the agency is in trouble. At best, an intelligence agency will have to spend more time and resources on legal matters than it normally would. At worst, programs that get information that can stop attacks, will be terminated by a court order.
Another danger is that litigation will expose details of how intelligence agencies work. Methods of gathering intelligence, and sources of intelligence, are the most valuable secrets a country has. Knowing how an agency collects intelligence enables people to do things to counter efforts to gather that intelligence. Sources can also be exposed via litigation. Since many of the groups the NSA currently tries to listen in on are willing to do things like fly airplanes into buildings, any source who is outed by litigation (or leaks) is in serious danger of getting killed. Dead men provide no intelligence. Worse yet, they become examples to other potential sources.
Finally, there is the danger that litigation will have a "chilling effect" on the intelligence community. In the past, leaks and controversies have often led American intelligence agencies to shun the use of human intelligence. Often, sources stopped cooperation out of fear that they would be exposed. Litigation holds that same potential with various forms of technical intelligence, particularly the interception of communications, which was apparently crucial in thwarting the recent plan to destroy airliners over the Atlantic.
The groups that have waged a relentless campaign against the intelligence community, and which secured this ruling are not the only winners. Terrorists will be the biggest beneficiaries of court rulings that leave intelligence agencies afraid to aggressively gather information due to fears of angering groups like the ACLU enough that they file lawsuits. – Harold C. Hutchison (firstname.lastname@example.org)
A federal judge in Detroit has recently ruled that the NSA's program to intercept and listen in on terrorist conversations is unconstitutional. This latest success by those waging lawfare against the intelligence community and the Department of Defense, could be the most damaging. The American Civil Liberties Union filed this suit, along with multiple individuals who claimed the program caused them professional difficulties.