On October 10, 2007, the federal district court for the Northern District of California granted a preliminary injunction blocking implementation of the Department of Homeland Security's (DHS) rule regarding Social Security no-match letters, which was to take effect on September 14, 2007. The injunction is to remain in effect until the court makes a final decision. The government will likely appeal the decision, but a final decision will probably not be made before the end of the year.

The final rule will affect millions of employees, and the Social Security Administration (SSA) had planned to begin sending letters to nearly 150,000 employers.

In granting the injunction, the court determined that the plaintiffs, which included both unions and business groups, had raised sufficient concerns regarding the no-match process such that injunctive relief was appropriate to prevent irreparable harm. These concerns include the possible termination of lawfully employed workers based on incorrect SSA records. The court further held that the threat of criminal prosecution included in the no-match rule's "safe harbor" provision reflects a major change in DHS policy, and that DHS failed to follow mandated administrative requirements to effect the change.