The Justice Department's practice of making bulk requests for email in criminal investigations has come under fire from a pair of federal judges who say the volume of irrelevant information swept up poses an intrusion into Americans' privacy.

In the past year, U.S. magistrate judges John Facciola in Washington, D.C., and David Waxse in Kansas City, Kan., have rejected or modified a number of applications for warrants to search people's emails and other electronic communications at Internet firms such as Google Inc. and Yahoo Inc.

The rulings go against the grain of a federal judiciary that has generally approved them, according to current and former law-enforcement officials. They also come against the backdrop of a legal and political debate over the scope of government surveillance that has raged since the National Security Agency's bulk collection of phone records was revealed last summer.

At issue is the Justice Department's two-step process of obtaining all emails and other electronic information in the accounts of a person under investigation, and then using names and keywords to sift through it in hopes of finding evidence of wrongdoing.

The judges have ruled the government needs to refine its requests to comply with the Fourth Amendment, which protects against unreasonable searches.