FBI counter-terrorism agents began issuing the secret letters, which don't require a judge's approval, after Congress passed the USA Patriot Act in the wake of the Sept. 11, 2001, attacks.
The letters are used to collect unlimited kinds of sensitive, private information, such as financial and phone records and have prompted complaints of government privacy violations in the name of national security. Many of Google's services, including its dominant search engine and the popular Gmail application, have become daily habits for millions of people.
In a ruling written May 20 and obtained Friday, U.S. District Court Judge Susan Illston ordered Google to comply with the FBI's demands.
But she put her ruling on hold until the 9th U.S. Circuit Court of Appeals could decide the matter. Until then, the Mountain View, Calif.-based company must comply with the letters unless it shows the FBI didn't follow proper procedures in making its demands for customer data in the 19 letters Google is challenging, she said.