A big ruling which could potentially be much bigger than it appears right now. That's because it means nothing as long as it is stayed on appeal. But were this ruling to ultimately stand, it would be a tremendous reining in of the NSA. Judge Richard Leon ruled that the government couldn't cite a single case where the collection program thwarted "an imminent terrorist attack." Imminent is the operative word there. That ruling doesn't say it didn't thwart attacks. It could be Leon is referring to the "ticking bomb" scenario, where authorities know of an active threat; a bomb, a planned gas release, etc.
But is that the threshold to which the government should be held? I do feel this program likely overreached, but I've been concerned about throwing the baby out with the bathwater. Leon's ruling appears it might do just that.