A new federal rule aimed at cracking down on companies that systematically hire undocumented workers has had a setback. The regulation, issued by the Dept. of Homeland Security, had been set to go into effect on Sept. 14, but a federal judge has temporarily blocked it.

The Aug. 31 order from Judge Maxine Chesney in the federal Northern District of California also bars the Social Security Administration from notifying some 140,000 companies about the rule until a hearing is held. 

Justice Dept. officials would not comment when asked if they would appeal the ruling.

The judge’s order responds to a lawsuit filed Aug. 29 by the AFL-CIO, American Civil Liberties Union and other groups to stop the rule from being implemented. On Oct. 1 another federal judge will consider the groups’ request to permanently strike down the regulation. 

In her ruling, Judge Chesney said that the groups challenging the rule raised “serious questions” about whether DHS overstepped its legal authority in issuing it.

Under the regulation, published in the Federal Register  on Aug. 15, companies that get “no match” letters indicating that an employee’s documents do not correspond with Social Security records have 90 days to resolve the discrepancy. If employers cannot do so, they must terminate the worker.

The AFL-CIO welcomed Chesney’s ruling. “Employers have historically used the Social Security Administration’s ‘no match’ letters to exploit workers, and this rule would only give them a stronger pretext for doing more of the same,” says AFL-CIO President John Sweeney.

Business organizations also oppose the rule, although they did not join the AFL-CIO lawsuit. In an Aug. 27 letter, the Essential Worker Immigration Coalition asked DHS and the Social Security Administration to halt the rule’s implementation for a “minimum of 180 days” so that questions can be clarified. The coalition includes the Associated General Contractors, Associated Builders and Contractors and American Subcontractors Association.