You don’t need to know. You can’t know.” That’s what Kathy Norris, a 60-year-old grandmother of eight, was told when she tried to ask court officials why, the day before, federal agents had subjected her home to a furious search.

The agents who spent half a day ransacking Mrs. Norris’ longtime home in Spring, Texas, answered no questions while they emptied file cabinets, pulled books off shelves, rifled through drawers and closets, and threw the contents on the floor.