The court ruled Monday that undocumented workers who use phony identification can't be considered identity thieves unless they knew they were using ID numbers from real people. Some officials at the Agriprocessors plant in Postville, where hundreds of illegal immigrants were arrested in a raid last year, face identity theft counts.

On Tuesday, U.S. District Court Judge Linda Reade allowed former human resources employee Laura Althouse to drop the guilty plea to identity theft she made in October. She still faces sentencing May 13 on a charge of conspiracy to harbor undocumented immigrants for financial gain.

Former Agriprocessors vice president Sholom Rubashkin also faces identity theft-related charges and has pleaded not guilty. His attorney Guy Cook said he will file "very soon" a motion to dismiss some of the counts against his client based on the Supreme Court ruling.

The high court's decision limits federal authorities' use of a 2004 law designed to get tough on identity thieves.

Authorities charged 270 illegal immigrants with identity theft following the raid at the Postville plant on May 12, 2008. They all accepted plea deals in which they agreed not to fight deportation.